Proportion and seasonality of blood parasites in animals in Mosul using the Veterinary Teaching Hospital Lab data

Several local studies have examined evidence of blood parasites in different animals in Mosul; however, information about the most prevalent parasite and the seasonality of the infection remains limited. The objective of the study conducted here was to investigate the proportion and seasonality of blood parasites in animals in Mosul using the Veterinary Teaching Hospital Lab data. Laboratory records for a period of 25 months were used for data retrieval. In all included animals, Giemsa-stained blood smears were examined by an attending clinical pathologist for the presence of parasites. Seasons were assigned on a basis of examination date, and the seasonality was quantified by estimating season-to-season ratio. The results indicated that 61.77% of examined animals were tested positive for blood parasites. The most evident parasites were Trypanosoma spp., Theileria spp., Babesia spp., and then Anaplasma spp., with evidence of mixed infection. The odds of the infection did not significantly vary in different age groups. There was a marked linear pattern in the seasonality of the infection with Trypanosoma spp. and Anaplasma spp. An increase of the infection during spring and autumn with Theileria spp. and Babesia spp. was also evident. In conclusion, infection with blood parasites in different animals in Mosul is common with substantial burden, the effect of age-related infection is negligible, and the seasonality of the infection is evident.

Frequency and factors associated of potential zoonotic pathogens (Borrelia spp., Rickettsia spp., Leishmania spp., and Anaplasma phagocytophilum) in equids in the state of Bahia, Brazil

BACKGROUND

Currently, various zoonotic diseases are classified as emerging or reemerging. Because equids have a direct relationship with various vectors, they are possibly more frequently exposed to zoonotic agents than are humans. The undeniable importance of diseases such as human granulocytic anaplasmosis, spotted fever, and leishmaniasis for both public and animal health, as well as the possibility of equids acting as sources, reservoirs, or even sentinels for these pathogens, justifies the detection of their frequency and factors associated with infection in equids from northeastern Brazil.

METHODS

Blood samples were collected from 569 equids (528 horses, 33 donkeys, and 8 mules), 516 from a rural area and 53 from an urban area. Pathogen detection was carried out as follows: Borrelia spp. and Rickettsia spp., serological analysis; Leishmania spp., serological analysis and polymerase chain reaction (PCR); Anaplasma phagocytophilum, PCR. Determination of associated factors was carried out through generalized linear models.

RESULTS

The frequencies of positivity for the pathogens observed in equids were as follows: Borrelia spp., 13.9% (79/569); Leishmania spp., 3.5% (20/569); Rickettsia spp. 33.4% (190/569). Regarding factors associated with infection, male sex was associated with protection against Borrelia spp.; donkeys and mules were associated with protection against Rickettsia spp., while a younger age was a risk factor. The infection of A. phagocytophilum was not detected in the sampled population. Co-infection was detected in 5.1% (29/569) of the animals.

CONCLUSIONS

Most of the studied pathogenic agents are present in the prospected area, indicating a possible risk for both human and animal health. This demonstrates that equids can be considered important sentinels in the assessment of pathogens with zoonotic potential in the region.

Innate Immune Response to Tick-Borne Pathogens: Cellular and Molecular Mechanisms Induced in the Hosts

Many pathogens are transmitted by tick bites, including Anaplasma spp., Ehrlichia spp., Rickettsia spp., Babesia and Theileria sensu stricto species. These pathogens cause infectious diseases both in animals and humans. Different types of immune effector mechanisms could be induced in hosts by these microorganisms, triggered either directly by pathogen-derived antigens or indirectly by molecules released by host cells binding to these antigens. The components of innate immunity, such as natural killer cells, complement proteins, macrophages, dendritic cells and tumor necrosis factor alpha, cause a rapid and intense protection for the acute phase of infectious diseases. Moreover, the onset of a pro-inflammatory state occurs upon the activation of the inflammasome, a protein scaffold with a key-role in host defense mechanism, regulating the action of caspase-1 and the maturation of interleukin-1β and IL-18 into bioactive molecules. During the infection caused by different microbial agents, very similar profiles of the human innate immune response are observed including secretion of IL-1α, IL-8, and IFN-α, and suppression of superoxide dismutase, IL-1Ra and IL-17A release. Innate immunity is activated immediately after the infection and inflammasome-mediated changes in the pro-inflammatory cytokines at systemic and intracellular levels can be detected as early as on days 2–5 after tick bite. The ongoing research field of “inflammasome biology” focuses on the interactions among molecules and cells of innate immune response that could be responsible for triggering a protective adaptive immunity. The knowledge of the innate immunity mechanisms, as well as the new targets of investigation arising by bioinformatics analysis, could lead to the development of new methods of emergency diagnosis and prevention of tick-borne infections.

Seroprevalence of viral and vector-borne bacterial pathogens in domestic dogs (Canis familiaris) in northern Botswana

BACKGROUND

Domestic dogs (Canis familiaris) have the potential to act as disease reservoirs for wildlife and are important sentinels for common circulating pathogens. Therefore, the infectious disease seroprevalence among domestic dogs in northern Botswana may be indicative of pathogen exposure of various wildlife species. The objective of this study was to assess the seroprevalence of Ehrlichia spp., Borrelia burgdorferi, Anaplasma spp., Dirofilaria immitis, canine adenovirus, canine parvovirus, and canine distemper virus in domestic dogs as proxies of disease prevalence in the local wildlife in the Okavango Delta region of Botswana. Statistical analysis assessed crude and factor-specific seroprevalence proportions in relation to age, sex, and geographical location as predictors of seropositivity. Logistic regression was used to identify adjusted predictors of seropositivity for each of the pathogens of interest.

RESULTS

Samples from 233 dogs in a total of seven locations in Maun, Botswana, and surrounding villages were collected and serologically analyzed. No dogs were seropositive for B. burgdorferi, while low seroprevalence proportions were observed for Anaplasma spp. (2.2%) and D. immitis (0.9%). Higher seroprevalence proportions were observed for the tick-borne pathogen Ehrlichia spp. (21.0%), and 19.7% were seropositive for canine adenovirus (hepatitis). The highest seroprevalence proportions were for canine parvovirus (70.0%) and canine distemper virus (44.8%). The predictors of seropositivity revealed that adults were more likely to be seropositive for canine adenovirus, canine distemper virus, and canine parvovirus than juveniles, and location was a risk factor for canine adenovirus, canine distemper virus, canine parvovirus, and Ehrlichia spp.

CONCLUSIONS

Results indicate that increasing tick control and vaccination campaigns for domestic dogs may improve the health of domestic animals, and potentially wildlife and humans in the Okavango Delta since viral and vector-borne bacterial pathogens can be transmitted between them.

First detection and molecular identification of the zoonotic Anaplasma capra in deer in France

Cervids are known to be reservoirs of zoonotic bacteria transmitted by ticks. This study aimed to identify the Anaplasma species carried by captive red deer and swamp deer in a wild fauna reserve in France. Blood from 59 red deer and 7 swamp deer was collected and analyzed over a period of two years. A semi-nested PCR targeting the 23S rRNA was performed to detect and characterize Anaplasma spp. and determine the presence of zoonotic species. Anaplasma phagocytophilum was identified in 14/59 red deer (23.7%) but it was not identified in any of the swamp deer (7 animals). Three sequences could not be assigned to any particular species based on the 23S rRNA sequences. Complementary nested PCR targeting 16S rRNA, gltA and groEL genes and sequencing analysis then identified these sequences as a recently reported zoonotic species, Anaplasma capra; this species was found in 2 red deer (Cervus elaphus) and 1 swamp deer (Rucervus duvaucelii). This is the first report of the tick-borne zoonotic bacterium A. capra in France, a species otherwise described only in China, Japan, Malaysia and South Korea in goats, sheep, deer, cattle and Japanese serows (Capricornis crispus). While this bacterium may have been introduced into the reserve by infected imported animals, its local epidemiological cycle via tick transmission seems possible as locally born deer were found infected. Diagnostic methods, especially molecular ones, should take into account the potential infection of animals and humans with this species.

A survey of argasid ticks and tick-associated pathogens in the Peripheral Oases around Tarim Basin and the first record of Argas japonicus in Xinjiang, China

Argasid ticks (Acari: Argasidae) carry and transmit a variety of pathogens of animals and humans, including viruses, bacteria and parasites. There are several studies reporting ixodid ticks (Acari: Ixodidae) and associated tick-borne pathogens in Xinjiang, China. However, little is known about the argasid ticks and argasid tick-associated pathogens in this area. In this study, a total of 3829 adult argasid ticks infesting livestock were collected at 12 sampling sites of 10 counties in the Peripheral Oases, which carry 90% of the livestock and humans population, around the Tarim Basin (southern Xinjiang) from 2013 to 2016. Tick specimens were identified to two species from different genera by morphology and sequences of mitochondrial 16S rRNA and 12S rRNA were derived to confirm the species designation. The results showed that the dominant argasid ticks infesting livestock in southern Xinjiang were Ornithodoros lahorensis (87.86%, 3364/3829). Ornithodoros lahorensis was distributed widely and were collected from 10 counties of southern Xinjiang. Argas japonicus was collected from Xinjiang for the first time. In addition, we screened these ticks for tick-associated pathogens and showed the presence of DNA sequences of Rickettsia spp. of Spotted fever group and Anaplasma spp. in the argasid ticks. This finding suggests the potential role for Argas japonicus as a vector of pathogens to livestock and humans.

Human-pathogenic Anaplasma spp., and Rickettsia spp. in animals in Xi'an, China

In China, thirteen species of tick-borne rickettsiales bacteria pathogenic to human have been reported in ticks and host animals, and human patients caused by them also has been identified. However, investigation for rickettsiales bacteria circulating in Xi'an wasn't performed although diseases resembling human diseases caused by these organisms have been found. In this study, domestic animals and ticks in Xi'an, China, were tested for the presence of rickettsiales bacteria pathogenic to humans. Besides A. ovis, a high prevalence of A. capra was observed suggesting a high public health risk exists. In addition, two novel Anaplasma species closely related to A. phagocytophilum were identified and formed distinct lineages in the phylogenetic trees, with more than 98.3% identities for rrs gene, while divergences up to 20.2% and 37.0% for groEL and gltA genes, respectively. Both of these two novel Anaplasma species were found to circulate in goats and further assessment of their pathogenicity is needed. Ca. R. jingxinensis, with potential pathogenicity, was also detected in H. longicomis ticks with high prevalence. However, other causative agents were not identified although they were distributed in other areas of China.

First detection of tick-borne pathogens of dogs from Malta

The knowledge about the vector-borne infections in domestic dogs has been increasing worldwide. However no studies have been done on hard tick infestation and tick-borne pathogens (TBPs) of dogs present in Malta. Therefore, a total of 99 dogs was selected and inspected between March and July 2013 in 18 urban and 17 rural areas on the islands of Malta and Gozo. All ticks were removed from the dogs and identified. Blood samples were taken and tested for protozoa (Babesia spp. and Hepatozoon spp.) and bacteria (Anaplasma spp., Ehrlichia spp., Rickettsia spp.) by conventional PCR. All of the ticks collected from 34 (34.3%; 95% CI: 26-44) dogs belong to the species Rhipicephalus sanguineus sensu lato. Tick infestation on the farm dogs was significantly higher than that of dogs kept outdoors as pets (OR: 15.19, 95% CI: 2.72-118.92, p<0.001) or in a sanctuary (OR: 35.11, 95% CI: 3.20-1986.67, p<0.001). Altogether 22 animals were infected with one or two TBPs, most of them with Hepatozoon canis (16/22; 72.7%). Anaplasma platys and Babesia vogeli were detected in 5 and 4 dogs, respectively. Three dogs had co-infections caused by H. canis and A. platys. To the best of our knowledge, this is the first report on tick infestation and TBPs of dogs in Malta.

Comparative Experimental Infection Study in Dogs with Ehrlichia canis, E. chaffeensis, Anaplasma platys and A. phagocytophilum

Dogs acquire infections with the Anaplasmataceae family pathogens, E. canis, E. chaffeensis, E. ewingii, A. platys and A. phagocytophilum mostly during summer months when ticks are actively feeding on animals. These pathogens are also identified as causing diseases in people. Despite the long history of tick-borne diseases in dogs, much remains to be defined pertaining to the clinical and pathological outcomes of infections with these pathogens. In the current study, we performed experimental infections in dogs with E. canis, E. chaffeensis, A. platys and A. phagocytophilum. Animals were monitored for 42 days to evaluate infection-specific clinical, hematological and pathological differences. All four pathogens caused systemic persistent infections detectible throughout the 6 weeks of infection assessment. Fever was frequently detected in animals infected with E. canis, E. chaffeensis, and A. platys, but not in dogs infected with A. phagocytophilum. Hematological differences were evident in all four infected groups, although significant overlap existed between the groups. A marked reduction in packed cell volume that correlated with reduced erythrocytes and hemoglobin was observed only in E. canis infected animals. A decline in platelet numbers was common with E. canis, A. platys and A. phagocytophilum infections. Histopathological lesions in lung, liver and spleen were observed in all four groups of infected dogs; infection with E. canis had the highest pathological scores, followed by E. chaffeensis, then A. platys and A. phagocytophilum. All four pathogens induced IgG responses starting on day 7 post infection, which was predominantly comprised of IgG2 subclass antibodies. This is the first detailed investigation comparing the infection progression and host responses in dogs after inoculation with four pathogens belonging to the Anaplasmataceae family. The study revealed a significant overlap in clinical, hematological and pathological changes resulting from the infections.

Genetic systems for studying obligate intracellular pathogens: an update

Rapid advancements in the genetic manipulation of obligate intracellular bacterial pathogens have been made over the past two years. In this paper we attempt to summarize the work published since 2011 that documents these exciting accomplishments. Although each genus comprising this diverse group of pathogens poses unique problems, requiring modifications of established techniques and the introduction of new tools, all appear amenable to genetic analysis. Significantly, the field is moving forward from a focus on the identification and development of genetic techniques to their application in addressing crucial questions related to mechanisms of bacterial pathogenicity and the requirements of obligate intracellular growth.

Prevalence of tick-borne pathogens in Ixodes ricinus and Dermacentor reticulatus ticks from different geographical locations in Belarus

Worldwide, ticks are important vectors of human and animal pathogens. Besides Lyme Borreliosis, a variety of other bacterial and protozoal tick-borne infections are of medical interest in Europe. In this study, 553 questing and feeding Ixodes ricinus (n = 327) and Dermacentor reticulatus ticks (n = 226) were analysed by PCR for Borrelia, Rickettsia, Anaplasma, Coxiella, Francisella and Babesia species. Overall, the pathogen prevalence in ticks was 30.6% for I. ricinus and 45.6% for D. reticulatus. The majority of infections were caused by members of the spotted-fever group rickettsiae (24.4%), 9.4% of ticks were positive for Borrelia burgdorferi sensu lato, with Borrelia afzelii being the most frequently detected species (40.4%). Pathogens with low prevalence rates in ticks were Anaplasma phagocytophilum (2.2%), Coxiella burnetii (0.9%), Francisella tularensis subspecies (0.7%), Bartonella henselae (0.7%), Babesia microti (0.5%) and Babesia venatorum (0.4%). On a regional level, hotspots of pathogens were identified for A. phagocytophilum (12.5–17.2%), F. tularensis ssp. (5.5%) and C. burnetii (9.1%), suggesting established zoonotic cycles of these pathogens at least at these sites. Our survey revealed a high burden of tick-borne pathogens in questing and feeding I. ricinus and D. reticulatus ticks collected in different regions in Belarus, indicating a potential risk for humans and animals. Identified hotspots of infected ticks should be included in future surveillance studies, especially when F. tularensis ssp. and C. burnetii are involved.

Serosurveillance for livestock pathogens in free-ranging mule deer (Odocoileus hemionus)

Routine disease surveillance has been conducted for decades in mule deer (Odocoileus hemionus) in California for pathogens shared between wildlife and domestic ruminants that may have implications for the animal production industry and wildlife health. Deer sampled from 1990 to 2007 (n = 2,619) were tested for exposure to six pathogens: bluetongue virus (BTV), epizootic hemorrhagic disease virus (EHDV), bovine viral diarrhea virus (BVDV), Leptospira spp., Anaplasma spp. and Brucella spp. We evaluated the relationship between exposure to these pathogens and demographic risk factors to identify broad patterns in seroprevalence across a large temporal and spatial scale. The overall seroprevalence for the entire study period was 13.4% for BTV, 16.8% for EHDV, 17.1% for BVDV, 6.5% for Leptospira spp., 0.2% for Brucella spp., and 17% for Anaplasma spp. Antibodies against BTV and EHDV were most prevalent in the deer populations of southern California. Antibodies against Leptospira spp. and Anaplasma spp. were most prevalent in coastal and central northern California whereas antibodies against BVDV were most prevalent in central-eastern and northeastern California. The overall seroprevalence for Anaplasma spp. was slightly lower than detected in previous studies. North and central eastern California contains large tracts of federal land grazed by livestock; therefore, possible contact between deer and livestock could explain the high BVDV seroprevalence found in these areas. Findings from this study will help to establish baseline values for future comparisons of pathogen exposure in deer, inform on long-term trends in deer population health and provide relevant information on the distribution of diseases that are shared between wildlife and livestock.

Associations between coinfection prevalence of Borrelia lusitaniae, Anaplasma sp., and Rickettsia sp. in hard ticks feeding on reptile hosts

An increasing number of studies reveal that ticks and their hosts are infected with multiple pathogens, suggesting that coinfection might be frequent for both vectors and wild reservoir hosts. Whereas the examination of associations between coinfecting pathogen agents in natural host-vector-pathogen systems is a prerequisite for a better understanding of disease maintenance and transmission, the associations between pathogens within vectors or hosts are seldom explicitly examined. We examined the prevalence of pathogen agents and the patterns of associations between them under natural conditions, using a previously unexamined host-vector-pathogen system--green lizards Lacerta viridis, hard ticks Ixodes ricinus, and Borrelia, Anaplasma, and Rickettsia pathogens. We found that immature ticks infesting a temperate lizard species in Central Europe were infected with multiple pathogens. Considering I. ricinus nymphs and larvae, the prevalence of Anaplasma, Borrelia, and Rickettsia was 13.1% and 8.7%, 12.8% and 1.3%, and 4.5% and 2.7%, respectively. The patterns of pathogen prevalence and observed coinfection rates suggest that the risk of tick infection with one pathogen is not independent of other pathogens. Our results indicate that Anaplasma can play a role in suppressing the transmission of Borrelia to tick vectors. Overall, however, positive effects of Borrelia on Anaplasma seem to prevail as judged by higher-than-expected Borrelia-Anaplasma coinfection rates.

Detection of Anaplasma phagocytophilum from Wild Boars and Deer in Japan

This study was conducted to determine the prevalence and geographic distribution of Anaplasma phagocytophilum, the causative agent of human granulocytic anaplasmosis, in wild deer and boars in Japan. We analyzed the blood samples of the study animals using PCR-targeting the 16S rDNA followed by DNA sequencing. Wild deer infected with Anaplasma spp., including Anaplasma bovis and Anaplasma centrale were detected in the region from Hokkaido to Kyushu. The infection rates of A. phagocytophilum, A. bovis, and A. centrale in deer were 15.6, 21.9, and 37.5%, respectively, and the corresponding infection rates in wild boar were 3.6, 17.9, and 3.6%, respectively. However, p44/msp2 genes specific to A. phagocytophilum were not detected among the 16S rDNA-positive samples on PCR analysis. In addition, the 16S rDNA sequences of A. phagocytophilum were 100% similar to those detected previously in the deer in Japan and 98.6% similar to those of A. phagocytophilum detected in the United States and Europe, and from the tick, Ixodes ovatus and Ixodes persulcatus in Japan. These findings suggested that the A. phagocytophilum-related sequences detected from deer and wild boars in Japan were different from those of typical A. phagocytophilum strains.

Evidence of the importance of host habitat use in predicting the dilution effect of wild boar for deer exposure to Anaplasma spp

Foci of tick-borne pathogens occur at fine spatial scales, and depend upon a complex arrangement of factors involving climate, host abundance and landscape composition. It has been proposed that the presence of hosts that support tick feeding but not pathogen multiplication may dilute the transmission of the pathogen. However, models need to consider the spatial component to adequately explain how hosts, ticks and pathogens are distributed into the landscape.

In this study, a novel, lattice-derived, behavior-based, spatially-explicit model was developed to test how changes in the assumed perception of different landscape elements affect the outcome of the connectivity between patches and therefore the dilution effect. The objective of this study was to explain changes in the exposure rate (ER) of red deer to Anaplasma spp. under different configurations of suitable habitat and landscape fragmentation in the presence of variable densities of the potentially diluting host, wild boar. The model showed that the increase in habitat fragmentation had a deep impact on Habitat Sharing Ratio (HSR), a parameter describing the amount of habitat shared by red deer and wild boar, weighted by the probability of the animals to remain together in the same patch (according to movement rules), the density of ticks and the density of animals at a given vegetation patch, and decreased the dilution effect of wild boar on deer Anaplasma ER.

The model was validated with data collected on deer, wild boar and tick densities, climate, landscape composition, host vegetation preferences and deer seropositivity to Anaplasma spp. (as a measure of ER) in 10 study sites in Spain. However, although conditions were appropriate for a dilution effect, empirical results did not show a decrease in deer ER in sites with high wild boar densities. The model showed that the HSR was the most effective parameter to explain the absence of the dilution effect. These results suggest that host habitat usage may weaken the predicted dilution effect for tick-borne pathogens and emphasize the importance of the perceptual capabilities of different hosts in different landscapes and habitat fragmentation conditions for predictions of dilution effects.

Tick-borne rickettsial pathogens in ticks and small mammals in Korea

In order to investigate the prevalence of tick-borne infectious agents among ticks, ticks comprising five species from two genera (Hemaphysalis spp. and Ixodes spp.) were screened using molecular techniques. Ticks (3,135) were collected from small wild-caught mammals or by dragging/flagging in the Republic of Korea (ROK) and were pooled into a total of 1,638 samples (1 to 27 ticks per pool). From the 1,638 tick samples, species-specific fragments of Anaplasma phagocytophilum (1 sample), Anaplasma platys (52 samples), Ehrlichia chaffeensis (29 samples), Ehrlichia ewingii (2 samples), Ehrlichia canis (18 samples), and Rickettsia rickettsii (28 samples) were amplified by PCR assay. Twenty-one pooled and individual tick samples had mixed infections of two (15 samples) or three (6 samples) pathogens. In addition, 424 spleen samples from small captured mammals (389 rodents, 33 insectivores, and 2 weasels) were screened for selected zoonotic pathogens. Species-specific DNA fragments of A. phagocytophilum (110 samples), A. platys (68 samples), E. chaffeensis (8 samples), E. ewingii (26 samples), E. canis (51 samples), and Rickettsia sp. (22 samples) were amplified by PCR assay. One hundred thirty small mammals had single infections, while 4, 14, and 21 striped field mice (Apodemus agrarius) had mixed infections of four, three, and two pathogens, respectively. Phylogenetic analysis based on nucleotide sequence comparison also revealed that Korean strains of E. chaffeensis clustered closely with those from China and the United States, while the Rickettsia (rOmpA) sequences clustered within a clade together with a Chinese strain. These results suggest that these agents should be considered in differential diagnosis while examining cases of acute febrile illnesses in humans as well as animals in the ROK.

Multiplex Detection of Ehrlichia and Anaplasma Pathogens in Vertebrate and Tick Hosts by Real-Time RT-PCR

Tick-borne rickettsial infections are responsible for many emerging diseases in humans and several vertebrates. These include human infections with Ehrlichia chaffeensis, Ehrlichia ewingii and Anaplasma phagocytophilum. As single or co-infections can result from a tick bite, the availability of a rapid, multiplex molecular test will be valuable for timely diagnosis and treatment. We recently described a muliplex-molecular test that can detect single or co-infections with up to five Ehrlichia and Anaplasma species. We reported that the test has the sensitivity to identify single infections in the canine host with E. chaffeensis, E. canis, E. ewingii, A. phagocytophilum, and A. platys and co-infection with E. canis and A. platys. In this study, ticks were collected from different parts of the state of Kansas during summer months of the year 2003 and tested for the presence of infection using the molecular test. The analysis revealed a minimum of 3.66% of the ticks to be positive for either E. chaffeensis or E. ewingii in A. americanum and Dermacenter species. This assay will be valuable in monitoring infections in dogs and ticks, and with minor modifications it can be used for diagnosing infections in people and other vertebrates.

Ehrlichia subversion of host innate responses

Anaplasma (formerly Ehrlichia) phagocytophilum and Ehrlichia chaffeensis, upon infection of humans, replicate in host leukocyte granulocytes and monocytes/macrophages, respectively. These unusual Gram-negative bacteria lack genes for biosynthesis of the lipopolysaccharide and peptidoglycan that activate host leukocytes. Caveolae-mediated endocytosis directs A. phagocytophilum and E. chaffeensis to an intracellular compartment secluded from oxygen-dependent and -independent killing. Furthermore, these bacteria orchestrate a remarkable series of events that culminate in suppression of NADPH oxidase, phagocyte activation and differentiation pathways, apoptosis, and interferon-gamma signaling in host leukocytes. They offer a fascinating example of how pathogens employ intricate strategies to usurp and subvert host cell function.

Anaplasma and Ehrlichia Infection

Human and animal infections by Anaplasmataceae are increasingly recognized as important and potentially fatal arthropod-transmitted diseases. Since the first recognition and implementation of diagnostic methods for human infection by Ehrlichia chaffeensis and Anaplasma phagocytophilum, the incidence of infections has linearly increased. Moreover, diagnostic and epidemiological testing indicates that "ehrlichia" infections are globally distributed and suggests that additional agents of human and veterinary "ehrlichiosis" will be identified. With increasing disease identification has come recognition that the infections can be severe, with approximately one-half of patients requiring hospitalization for complications including respiratory distress, myocarditis, neurological complications, hepatitis, a septic or toxic shock-like disease, opportunistic infections, and death in 0.5 to 3.0%. An understanding of the diseases, pathophysiology, pathogenesis, control, and management will best be developed through fundamental investigations. Advances in comprehension as to the separate contributions of bacteria and host are crucial since most data now suggest that alterations in host neutrophil function and protection from innate and adaptive immunity also contribute to disease manifestations. It is reasonable to operate from the hypothesis that these host cell functional changes ultimately benefit bacterial survival while inadvertently eliciting clinical disease in poorly adapted hosts. A firmer basis for the scientific understanding of Anaplasmataceae biology will allow logical and rational approaches toward infection control, prevention, and treatment.

Effects of Anaplasma phagocytophilum infection on the molting success of Ixodes scapularis (Acari: Ixodidae) larvae

We assessed the effects of sympatric (occupying the same or overlapping geographic areas) and allopatric (occurring in separate geographic areas) isolates of Anaplasma phagocytophilum on the survival of Ixodes scapularis Say larvae that were derived from ticks collected in Bridgeport, CT. Seven isolates of A. phagocytophilum, originating from different geographic regions of the United States, were tested: four isolates from the northeast (Bridgeport, Dawson, Gaillard, and NY-8), two from the Midwest (Webster and Sp-Is), and one from California (MRK). BALB/c mice were infected with each of the seven isolates via exposure to infected I. scapularis nymphs, whereas uninfected nymphs fed upon control mice. Both infected and control mice were infested with uninfected larvae at 1, 2, 3, 4, 6, and 9 wk after nymphal infestation. The molting success in cohorts of infected and uninfected ticks was calculated as the percentage of larvae successfully molting into nymphal stage, and the prevalence of infection in molted nymphs was determined by polymerase chain reaction. In ticks that became infected with the Bridgeport or Sp-Is isolates, the molting success decreased with an increase in the prevalence of infection. Ticks that fed upon mice infected with six allopatric isolates (Dawson, Gaillard, NY-8, Sp-Is, Webster, and MRK) showed significantly lower levels of survival than those fed upon control mice, regardless of the prevalence of infection, whereas in ticks fed upon mice infected with a sympatric isolate (Bridgeport), the overall molting success was similar to the control. Thus, some but not all of the A. phagocytophilum isolates have adverse effects on ticks. Ticks exposed to harmful isolates may experience higher levels of bacterial metabolism, and/or reduced quality of their blood meal, thereby reducing their survival. Noted differences between isolates may be due to the origin of a particular isolate and/or the degree of coadaptation between the pathogen and its vector on the population level.

Acarological risk of exposure to agents of tick-borne zoonoses in the first recognized Italian focus of Lyme borreliosis

Acarological risk was calculated as the probability of encountering at least one host-seeking Ixodes ricinus tick infected by the pathogen Borrelia burgdorferi sensu lato, in 100 m transects in the province of Genoa, Italy. The seasonal pattern of I. ricinus was studied using generalized estimating equations (GEE) with negative binomial error, to consider overdispersion of tick counts and repeated sampling of the same dragging sites from April 1998 to March 1999. Prevalence of infection by B. burgdorferi s.l. was evaluated by PCR and hybridization with genospecies-specific probes. Acarological risk (R) peaked in April (R = 0.2, 95% CI 0.13-0.26) and November (R = 0.29, 95% CI 0.10-0.46). Borrelia garinii and B. valaisiana were the most common genospecies at our study site suggesting a major role of birds as reservoirs. DNA from Anaplasma phagocytophilum, the agent of granulocytic ehrlichiosis in humans and animals, was amplified from an adult I. ricinus.

Conservation of a gene conversion mechanism in two distantly related paralogues of Anaplasma marginale

Anaplasmataceae, the causative agents of anaplasmosis and ehrlichiosis, persist in the bloodstream of their mammalian hosts, allowing acquisition and transmission by tick vectors. Anaplasma marginale establishes persistent infection characterized by sequential cycles of rickettsaemia in which new antigenic variants emerge. The two most immunodominant outer membrane proteins, MSP2 and MSP3, are paralogues, each encoded by a distinct family of related genes. This study demonstrates that, although the two gene families have diverged substantially, each has maintained a similar mechanism to generate structurally and antigenically polymorphic surface antigens. Like MSP2, MSP3 is expressed from a single locus in which variation of the expressed msp3 gene is generated by recombination using msp3 pseudogenes. Each of the msp3 pseudogenes encodes a unique central variable region (CVR) flanked by conserved 5' and 3' regions. Changes in the CVR of the expressed msp3, concomitant with invariance of the pseudogenes, indicate that expression site variation is generated using gene conversion. A. marginale thus maintains two large, separate systems within its small genome to generate antigenic variation of its surface proteins, while analogous structural elements indicate a common mechanism.

Applications of a cell culture system for studying the interaction of Anaplasma marginale with tick cells

A cell culture system for the tick-borne rickettsia Anaplasma marginale offers new opportunities for research on this economically important pathogen of cattle. A. marginale multiplies in membrane-bound inclusions in host cells. Whereas erythrocytes appear to be the only site of infection in cattle, A. marginale undergoes a complex developmental cycle in ticks and transmission occurs via the salivary glands during feeding. We recently developed a cell culture system for A. marginale using a cell line derived from embryos of Ixodes scapularis. Here we review the use of this cell culture system for studying the interaction of A. marginale with tick cells. Several assays were developed using the A. marginale/tick cell system. An adhesion assay was developed for the identification of proteins required by A. marginale for adhesion to tick cells. The effect of antibodies against selected major surface proteins in inhibiting A. marginale infection was tested in an assay that allowed further confirmation of the role of surface proteins in the infection of tick cells. A drug screening assay for A. marginale was developed and provides a method of initial drug selection without the use of cattle. The culture system was used to test for enhancing effects of tick saliva and saliva components on A. marginale infection. The tick cell culture system has proved to be a good model for studying A. marginale-tick interactions. Information gained from these studies may be applicable to other closely related tick-borne pathogens that have been propagated in the same tick cell line.

Major histocompatibility complex class II DR-restricted memory CD4(+) T lymphocytes recognize conserved immunodominant epitopes of Anaplasma marginale major surface protein 1a

Native major surface protein 1 (MSP1) of Anaplasma marginale, composed of covalently associated MSP1a and MSP1b proteins, stimulates protective immunity in cattle against homologous and heterologous strain challenge. Protective immunity against pathogens in the family Anaplasmataceae involves both CD4(+) T cells and neutralizing immunoglobulin G. Thus, an effective vaccine should contain both CD4(+) T- and B-lymphocyte epitopes that will elicit strong memory responses upon infection with homologous and heterologous strains. Previous studies demonstrated that the predominant CD4(+) T-cell response in MSP1 vaccinates is directed against the MSP1a subunit. The present study was designed to identify conserved CD4(+) T-cell epitopes in MSP1a presented by a broadly represented subset of major histocompatibility complex (MHC) class II molecules that would be suitable for inclusion in a recombinant vaccine. Transmembrane protein prediction analysis of MSP1a from the Virginia strain revealed a large hydrophilic domain (HD), extending from amino acids (aa) 1 to 366, and a hydrophobic region extending from aa 367 to 593. The N terminus (aa 1 to 67) includes one 28-aa form A repeat and one 29-aa form B repeat, which each contain an antibody neutralization-sensitive epitope [Q(E)ASTSS]. In MSP1 vaccinates, recombinant MSP1a HD (aa 1 to 366) stimulated recall proliferative responses that were comparable to those against whole MSP1a excluding the repeat region (aa 68 to 593). Peptide mapping determined a minimum of five conserved epitopes in aa 151 to 359 that stimulated CD4(+) T cells from cattle expressing DR-DQ haplotypes common in Holstein-Friesian breeds. Peptides representing three epitopes (aa 231 to 266, aa 270 to 279, and aa 290 to 319) were stimulatory for CD4(+) T-cell clones and restricted by DR. A DQ-restricted CD4(+) T-cell epitope, present in the N-terminal form B repeat (VSSQSDQASTSSQLG), was also mapped using T-cell clones from one vaccinate. Although form B repeat-specific T cells did not recognize the form A repeat peptide (VSSQS_EASTSSQLG), induction of T-cell anergy by this peptide was ruled out. The presence of multiple CD4(+) T-cell epitopes in the MSP1a HD, in addition to the neutralization-sensitive epitope, supports the testing of this immunogen for induction of protective immunity against A. marginale challenge.

Immunization of cattle with Anaplasma marginale derived from tick cell culture

Anaplasmosis is a hemolytic disease of cattle caused by the ehrlichial tick-borne pathogen Anaplasma marginale. Killed vaccines used for control of anaplasmosis in the US used antigen harvested from infected bovine erythrocytes which was often contaminated with bovine cells and other pathogens. In this study, we performed an initial cattle trial to test A. marginale harvested from tick cell culture as an immunogen for cattle. Eleven yearling Holstein cattle were immunized with the cell culture-derived A. marginale and 11 cattle were non-immunized contact controls. Each vaccine dose contained approximately 2 x 10(10) A. marginale in an oil-based adjuvant. Two immunizations were administered subcutaneously 4 weeks apart and the cattle were challenge-exposed 10 weeks after the second immunization with A. marginale infected blood. Maximum antibody levels as determined by an A. marginale specific competitive ELISA were observed 2 weeks after the last immunization. Antibody responses against major surface proteins (MSPs) 1a and 1beta1 were also characterized and immunized cattle demonstrated a preferential recognition for MSP1beta1. Cattle immunized with the cell culture-derived A. marginale had a significantly lower percent reduction in the packed cell volume (P<0.05) after challenge exposure as compared with the controls and did not display clinical anaplasmosis. The cell culture-derived A. marginale shows promise for use as antigen in development of a new killed vaccine for anaplasmosis.

Anaplasma marginale inactivated vaccine: dose titration against a homologous challenge

The present study was performed to dose-titrate an Anaplasma marginale experimental immunogen derived from partially purified initial bodies from three geographically different Mexican strains. Three five-bovine groups were inoculated twice on days zero and 21 with A. marginale initial bodies equivalent to 1.5 x 10(10) (group I), 3 x 10(10) (group II) or 6 x 10(10) (group III) infected erythrocytes mixed with STDCM adjuvant. A similar group served as non-vaccinated controls. All four groups were challenged with 1 x 10(8) infected erythrocytes from a donor cow with an increasing rickettsemia of strain MEX-15 on day 87 post-vaccination. The prepatent period was very similar for all four groups. All five non-vaccinated controls presented typical acute anaplasmosis syndrome reaching a mean of 30.9% rickettsemia and a loss of 73.4% in the packed cell volume (PCV). Two of five controls died of acute anaplasmosis. Within the vaccinated groups only one animal (group II) suffered acute disease and died. Although all the other vaccinated animals were free of clinical signs, they developed very low rickettsemias (3.2, 3.8 and 4.3%) and PCV losses of 49.9, 47.8, and 49.3% for groups I, II and III. The starting mean weight was very similar for all four groups. All animals lost weight following challenge but losses for groups I and II were lower and significantly different from group IV losses (P < or = 0.1). Although there were no significant differences among vaccinated groups, group III was more severely affected. Taken altogether, these results show a 93.3% protection against both illness and death for all groups; and 100% protection for groups I and III, and 80% for group II.

Antigenic variation in vector-borne pathogens

Several pathogens of humans and domestic animals depend on hematophagous arthropods to transmit them from one vertebrate reservoir host to another and maintain them in an environment. These pathogens use antigenic variation to prolong their circulation in the blood and thus increase the likelihood of transmission. By convergent evolution, bacterial and protozoal vector-borne pathogens have acquired similar genetic mechanisms for successful antigenic variation. Borrelia spp. and Anaplasma marginale (among bacteria) and African trypanosomes, Plasmodium falciparum, and Babesia bovis (among parasites) are examples of pathogens using these mechanisms. Antigenic variation poses a challenge in the development of vaccines against vector-borne pathogens.

Interleukin-12 as an adjuvant promotes immunoglobulin G and type 1 cytokine recall responses to major surface protein 2 of the ehrlichial pathogen Anaplasma marginale

Anaplasma marginale is a tick-transmitted pathogen of cattle closely related to the human ehrlichiae, Ehrlichia chaffeensis and the agent of human granulocytic ehrlichiosis (HGE). These pathogens have in common a structurally conserved outer membrane protein (OMP) designated the major surface protein 2 (MSP-2) in A. marginale and HGE and OMP-1 in E. chaffeensis. Protective immunity against ehrlichial pathogens is believed to require induction of gamma interferon (IFN-gamma) and opsonizing immunoglobulin (Ig) subclasses directed against OMP epitopes that, in concert, activate macrophages for phagocytosis and killing. Because interleukin-12 (IL-12) acts as an adjuvant for protein immunization to induce IFN-gamma and protective immunity against intracellular pathogens, we hypothesized that as an adjuvant with MSP-2, IL-12 would augment type 1 recall responses to A. marginale. IL-12 was coadsorbed with MSP-2 to alum and shown to significantly enhance IFN-gamma production by lymph node cells (LNC) and LNC-derived CD4(+) T-cell lines from immunized calves following recall stimulation with A. marginale. LNC proliferation and IL-2 production were also enhanced in IL-12-treated calves. Elevated recall proliferative responses by peripheral blood mononuclear cells were still evident 9 months after immunization. Serum IgG levels were consistently increased in IL-12 immunized calves, predominantly due to higher IgG1 responses. The results support the use of IL-12 coadsorbed with OMP of ehrlichial pathogens in alum to amplify both antibody and type-1 cytokine responses important for protective immunity.

Evaluation of Anaplasma marginale from tick cell culture as an immunogen for cattle

Anaplasma marginale has been propagated and continuously passaged in an Ixodes scapularis cell line. Anaplasma development was characterized and cultures with a high density of rickettsiae were harvested at a predictable rate. Culture-derived A. marginale (CAM) remained infective for cattle and was used effectively as antigen in diagnostic tests with the sensitivity to identify bovine carriers of A. marginale. This study presents results of an initial trial using the CAM as an immunogen for cattle. CAM was mechanically disrupted, frozen at -70 degrees C, and inactivated with beta-propiolactone. Two intact yearling cattle were immunized with CAM and Freund's adjuvant, receiving 4 subcutaneous injections at 3-4 week intervals. Two control yearling cattle received adjuvant and PBS. Serum samples were evaluated by competitive ELISA (C-ELISA) using CAM as antigen and the standard complement fixation test (CFT). All cattle were subsequently challenged with A. marginale-infected blood from a carrier cow. An additional intact calf was inoculated with live CAM from the same passage and screened by C-ELISA and CFT. Sera collected from immunized cattle were negative or suspicious by CFT throughout the immunization study. The same sera were strongly positive by C-ELISA two weeks after the first injection and throughout the study. All cattle became infected following challenge-exposure with blood, but immunized cattle exhibited longer prepatent periods as well as lower parasitemias and percent reduction of packed cell volumes as compared with the controls. The calf receiving live CAM became infected and underwent a mild clinical reaction with positive C-ELISA and CFT results and did not become clinically ill following blood challenge. This preliminary study suggests that the CAM antigen is highly immunogenic in cattle. Furthermore, the CFT did not identify immunized animals whereas the C-ELISA (using CAM) was highly sensitive for detection of both immunized and infected animals.

Characterization of Anaplasma isolates from eland (Taurotragus oryx). Pathogenicity in cattle and sheep and DNA profiles analysis

Two eland Anaplasma isolates, AnapE1, from Kenya, and AnapE2, from South Africa were characterised. Their characterization was based on their pathogenicity to intact and splenectomized cattle and sheep and also their DNA profiles. Their DNA profiles were analysed and compared to Anaplasma marginale, A. ovis and A. centrale after endonuclease restrictions and probing with Anaplasma DNA probes, AC5-12 and AC-1. The results of the pathogenicity trials showed AnapE1 to be similar to A. ovis and AnapE2 an isolate of A. marginale. On DNA profiles, AnapE1 was close to A. ovis, with differences that occur even in same Anaplasma species isolates from different locations. On the other hand, AnapE2, resembled one of the A. marginale isolates known to occur in South Africa. The DNA profiles correlated well with the pathogenicity results. It is concluded that elands are carriers of both A. marginale and A. ovis parasites and are therefore important reservoirs that need attention in epidemiology of anaplasmosis.

Effect of breed of cattle on innate resistance to infection with Babesia bovis, B bigemina and Anaplasma marginale

OBJECTIVE

To assess the innate resistance of naive Bos taurus, Bos taurus cross Bos indicus and Bos indicus cattle to virulent Babesia bovis, B bigemina and Anaplasma marginale parasites.

DESIGN

Groups of 10, pure B indicus, 1/2 B indicus cross, 1/4 B indicus cross and pure B taurus steers were infected with virulent B bovis, B bigemina and A marginale parasites [corrected].

PROCEDURE

Sequential infections were carried out by intravenous inoculation of infected blood containing 1 x 10(8) parasites of B bovis, followed by B bigemina and then A marginale. To assess resistance, measurements were made of parasitaemia, rectal temperature, packed cell volume and the number within a group requiring chemotherapy to control infection. There was a recovery period between each infection.

RESULTS

Infection with B bovis showed that pure B indicus steers were significantly more resistant to B bovis infection than the other groups, with none of this group requiring treatment. There was no significant difference between 1/2 B indicus cross and 1/4 B indicus cross with 30% and 20%, respectively, of steers in these groups requiring treatment [corrected]. The pure B taurus steers were significantly more affected then those in the other three groups with 80% requiring treatment. Infections of B bigemina produced a mild response in comparison to that of B bovis and none of the steers required treatment. However, the pure B taurus group was significantly more affected than the other three groups for all other measurements. After the A marginale infection, B indicus steers were moderately affected with 50% requiring treatment, whereas 70% of the 1/2 B indicus group, 80% of the 1/4 B indicus cross group and 100% of the pure B taurus group required treatment [corrected].

CONCLUSIONS

All breeds of cattle, ranging from pure B indicus to pure B taurus may be at risk of severe disease if exposed to virulent A marginale. The results confirm that pure B indicus cattle are relatively resistant to B bovis, but there could be a significant risk of severe mortalities if cross-bred herds are exposed to virulent infection.

Characterization of hemagglutinating components on the Anaplasma marginale initial body surface and identification of possible adhesins

Interaction of Anaplasma marginale initial bodies with the bovine erythrocyte surface was examined by a direct hemagglutination assay. Purified initial bodies were shown to specifically hemagglutinate bovine erythrocytes but not erythrocytes from nonhost animal species. Hemagglutination was inhibited by treatment of purified initial bodies with trypsin, alpha-chymotrypsin, or proteinase K but not by treatment with neuraminidase or sodium periodate. Treatment of bovine erythrocytes with alpha-chymotrypsin or neuraminidase partially inhibited hemagglutination of the treated cells by initial bodies. In contrast, no inhibition occurred after treatment of erythrocytes with trypsin, phospholipases, or sodium periodate or when monosaccharides and disaccharides were used as potential competitive inhibitors. Thus, the initial body receptor is probably a surface protein, whereas the bovine receptor may comprise both protein and carbohydrate. Hemagglutination was unaffected by treatment of initial bodies with monoclonal or polyclonal antibodies raised against the A. marginale 31-kDa (MSP4) major surface polypeptide or non-A. marginale proteins or by treatment with a monoclonal antibody to the A. marginale MSP1a neutralization-sensitive epitope. In contrast, antiserum raised against whole A. marginale initial bodies or monospecific antibodies raised against purified A. marginale major surface polypeptides with molecular sizes of 105 (MSP1a), 100 (MSP1b), 61, and 36 (MSP2) kDa completely or partially inhibited hemagglutination. These data confirm the proposed surface location of the proteins susceptible to inhibition and suggest that they mediate hemagglutination of bovine erythrocytes. We propose that these surface proteins are possible adhesins.

Development and infectivity of Anaplasma marginale in Dermacentor andersoni nymphs

The development of Anaplasma marginale was studied in Dermacentor andersoni nymphs after they had fed on a calf with ascending Anaplasma infection. Gut tissues were collected on day 4 of tick feeding, from newly replete (fed) nymphs and on postfeeding days (PFD) 5, 10, 15, 20, and were processed for light and electron microscopy to determine density of A marginale colonies. Homogenates of gut tissues were prepared from nymphs collected on the same days and inoculated into susceptible, splenectomized calves to test for infectivity. Anaplasma colonies were detected in gut cells on PFD 5, 10, 15, and 20. Although colony density appeared to be higher on PFD 10 and 15, differences were not significant. Nymphal type-1 colonies were detected in highest numbers on PFD 5 and 10, transitional colonies were seen in highest numbers at PFD 10 and 15, and nymphal type-2 colonies were observed only on PFD 20. Gut homogenates that were collected from ticks at 4 days of feeding, when newly replete, and on PFD 20 caused anaplasmosis when injected into susceptible calves, but homogenates made from ticks collected on PFD 5, 10, and 15 were not infective. The data indicate that of the colony types of A marginale that develop in replete nymphs, nymphal type-1 and transitional colonies may contain organisms that are not infective for cattle.

Infectivity and antigenicity of Anaplasma marginale from tick cell culture

The infectivity and immunogenicity of Anaplasma marginale grown in a tick cell culture from embryonic Dermacentor variabilis ticks were assessed in splenectomized and intact calves, respectively. Culture 1 consisted of the cell line inoculated with midguts of adult ticks infected with the Mississippi isolate of A marginale and dissected 5 to 10 days after repletion and detachment from an experimentally infected calf. Cultures 2 and 3 consisted of the cell line inoculated with midguts of ticks infected with the Virginia isolate of the organism. Inoculum for culture 2 was derived from nymphal ticks dissected 5 to 10 days after repletion and detachment from the infected calf; inoculum for culture 3 was midguts from adult ticks that were fed as nymphs, allowed to molt in the laboratory and dissected 21 to 24 days after molting. In trial 1, cultures 1, 2, and 3 were maintained at pH 6.9 and incubated at 28 C; in trial 2, cultures 1 and 3 were maintained at pH 7.4 and incubated at either 28 C or 37 C. Cultures 1, 2, and 3 failed to induce infection when injected IV and SC into 6 calves in 2 separate trials. Pre-challenge sera from these calves reacted with 2 purified Anaplasma antigens in the ELISA, but failed to react in the complement-fixation test. Results of a trial to use cultures 1 and 3 in combination with an oil-in-water adjuvant to immunize intact calves against A marginale were inconclusive. However, pre-challenge sera from immunized calves reacted with the 2 purified Anaplasma initial body antigens in the ELISA but failed to react in the complement-fixation text.(ABSTRACT TRUNCATED AT 250 WORDS)

Characteristics of an attenuated Anaplasma marginale of deer origin as an anaplasmosis vaccine

A fully virulent field Anaplasma marginale isolate, passaged to a splenectomised white tailed deer, lost virulence for cattle after 18 months in the non-bovine host. This attenuated A. marginale produced a mild response in four 18-month-old Holstein steers characterised by an average 2.4% parasitaemia, a 13% drop in PCV and a positive serological response. All vaccinated steers were immune to challenge with a fully virulent, heterologous A. marginale when compared with non-vaccinated controls.

Experimental anaplasmosis in mule deer: persistence of infection of Anaplasma marginale and susceptibility to A. ovis

An experimental Anaplasma marginale infection was induced in a splenectomized mule deer (Odocoileus hemionus hemionus) which persisted subclinically at least 376 days as detected by subinoculation into susceptible cattle. Anaplasma ovis was experimentally transmitted from sheep to a splenectomized and a spleen-intact mule deer, and back to sheep. The pathogenesis in deer was very similar to that seen in sheep using ovine blood inoculations.

Infectivity of three Anaplasma marginale isolates for Dermacentor andersoni

Three isolates of Anaplasma marginale--Virginia (VAM), Illinois (IAM), and Florida (FAM)--were compared for infectivity for Dermacentor andersoni. The isolates were selected, in part, because of a tail-like appendage that has been demonstrated in the VAM and IAM, but not in the FAM. Ticks were exposed to the isolates as nymphs either naturally by feeding on a calf with anaplasmosis or artificially by percutaneous inoculation with infected bovine erythrocytes. They were examined for infectivity after molting to the adult stage by determining their capability to transmit the disease to susceptible calves and by demonstrating colonies in tick gut sections. Only those ticks exposed to the VAM proved to be infected with A marginale; ticks naturally exposed and those artificially infected with this isolate transmitted the disease to susceptible calves. Colonies of A marginale were observed only in gut tissues of ticks naturally infected with VAM. The IAM (appendage present) and FAM (appendage absent) could not be found in ticks exposed by either method, indicating that factors other than the presence of inclusion appendages may be involved in infection of ticks by A marginale.

Experimental anaplasmosis in American bison: persistence of infections of Anaplasma marginale and non-susceptibility to A. ovis

Blood collected 314 and 496 days after experimentally infecting splenectomized and spleen-intact American bison (Bison bison) with Anaplasma marginale was infective for splenectomized bovine steers. The pathogenesis was identical to that seen in bovine studies using bovine blood inoculations. A splenectomized bison remained normal clinically, hematologically and serologically for 10 mo after repeated inoculation of ovine blood infected with A. ovis.

Epidemiologic aspects of bovine anaplasmosis in semiarid range conditions of south central Idaho

The prevalance of Anaplasma marginale-infected cows, as determined by use of the modified rapid card agglutination (MRCA) test, was measured during a 4-year period (1980-1983). The prevalence of A marginale-infected cows, defined as positive reactors on the MRCA test, remained constant (31%-37%). The apparent incidence of A marginale transmission to susceptible cows was approximately 7% from 1980 to 1981, 8% from 1981 to 1982, and no transmission from 1982 to 1983. The occasional MRCA-positive cow became negative on the MRCA test, and 1 cow was determined to be free of A marginale infection by subinoculation of 100 ml of the cow's blood into a susceptible, splenectomized calf. Dermacentor andersoni, a known vector of A marginale, was often found on the cattle and in their environment. However, A marginale was not transmitted to susceptible, splenectomized calves, using collected ticks. Of 56 calves born to MRCA-positive cows, 82% were MRCA-positive within the first 3 months of life. These calves converted to MRCA-negative status and were determined to be free of A marginale infection by subinoculation of their blood into susceptible, splenectomized calves, indicating the passive transfer of colostral antibodies.

Field observations on adult zebu bulls immunised against anaplasmosis by infection and treatment plus integrated tick control

Fourteen adult zebu bulls which were negative for Anaplasma marginale infection both serologically and on blood smear examinations were infected with a virulent Nigerian isolate of A. marginale. Forty days following the immunising infection when clinical reactions were established groups of seven animals were treated with either two doses of imidocarb dipropionate (2 X 5 mg/kg given intramuscularly 14 days apart) or a single intramuscular dose of long-acting oxytetracycline (5 mg/kg). Following clinical recovery, two weeks after the first treatment the immunised animals and seven susceptible controls were then introduced into a tick-infested area and held there for 15 months with regular tick control. There were significant differences between the mean weight gains of surviving animals in the oxytetracycline group and the controls and surviving animals in the imidocarb group and control cattle. The protective effect of tick control alone was inferior to that of integrated tick control plus anaplasmosis control by either method of immunisation. Losses occurred in all groups due mainly to the effects of other tick-borne diseases, babesiosis and heartwater.

Serologic and clinical responses of premunized, vaccinated, and previously infected cattle to challenge exposure by two different Anaplasma marginale isolates

Two Anaplasma marginale isolates, one originating in Florida (FAM) and the other from Virginia (VAM), were compared immunologically by cross-challenge exposure of 14 Anaplasma carrier cattle, 8 previously infected cattle, and 6 splenectomized carrier calves. In addition, 28 cattle vaccinated with a commercially available adjuvant killed vaccine and 22 nonvaccinated cattle were challenge exposed with either FAM or VAM. A detectable clinical response was not produced by either FAM or VAM challenge exposure in carrier and previously infected cattle; however, evidence of A marginale growth as characterized by low percentages of parasitemia and increased serum complement-fixation titers was seen in carrier cattle given a heterologous challenge organism and in previously infected cattle inoculated with either homologous or heterologous organisms. Among splenectomized calves, there was virtually no cross protection to the heterologous challenge exposure, whereas a homologous challenge failed to elicit any detectable response. Vaccinated cattle were resistant to VAM exposure, but the clinical response to FAM exposure was severe with a 47% mortality. Most of these cattle displayed typical acute anaplasmosis that was only marginally less severe than that encountered in nonvaccinated cattle.

Serologic comparisons of 4 Anaplasma isolates as measured by the complement-fixation test

Anaplasma marginale isolated from Virginia ( VAM ), from North Texas ( NTAM ), from Florida (FAM), and Anaplasma ovis from Idaho were used in these trials. Complement-fixation antigens from each of the 4 isolates were used to compare complement-fixing antibody titers of 10 cattle infected with VAM , 17 with FAM, and 6 with NTAM . Strong cross-reactions occurred with all antigens and sera. The homologous system generally showed higher average antibody titers. The serum antibody titers occurring with the A. ovis antigen were significantly lower than those seen with A. marginale antigens. Serum antibody titer differences as measured by FAM and NTAM antigens on sera from VAM , NTAM and FAM failed to reach significance. Serum antibody titer comparisons using VAM antigen were significantly different from those occurring with FAM and NTAM in most instances.

Anaplasma infections in wild and domestic ruminants: a review

Anaplasma marginale can be transmitted, will grow and can survive in a large number of domestic and wild animals. It is pathogenic in cattle, and usually produces nonapparent or mild infections in other species. Anaplasma marginale has been recovered from cattle, sheep, goats, water buffalo (Bubalus bubalis), white-tailed deer (Odocoileus virginianus), mule deer (Odocoileus hemionus hemionus), black-tailed deer (Odocoileus hemionus columbianus), pronghorn (Antilocapra americana americana), Rocky Mountain elk (Cervus elaphus nelsoni), bighorn sheep (Ovis canadensis canadensis), black wildebeest (Connochaetes gnu), blesbuck (Damaliscus albifrons), and duiker (Sylvicapra grimmi grimmi). Unidentified anaplasms have been seen in, and in some instances isolated from, Cape buffalo (Syncerus caffer), giraffe (Giraffa camelopardalis), wildebeest (Connochaetes taurinus), Cokes hartebeest (Alcelaphus buselaphus cokii), Thompson's gazelle (Gazella thompsonii), waterbuck (Kobus ellipsiprymnus), and sable antelope (Hippotragus niger), with serological evidence of Anaplasma infection in an even wider range of wild ruminant species. Anaplasma ovis, A. centrale, or other as yet unidentified anaplasms may well occur in other ruminants. With the exception of black-tailed deer, the epidemiologic significance of anaplasmosis in wildlife has yet to be determined. The only wild animal in which Anaplasma is reported to produce serious clinical disease is the giraffe.

Influence of increased temperature on Anaplasma marginale Theiler in the gut of Dermacentor andersoni stiles

Three splenectomized dairy calves were inoculated with a Virginia isolate of Anaplasma marginale Theiler and served as an infective source for laboratory-reared Dermacentor andersoni Stiles nymphs. One month after molting, groups of adult ticks were incubated at 37 C for 0, 1.5, 2.5, and 7 days. Gut homogenates were made from ticks representing each incubation period. Twenty-four susceptible, splenectomized dairy calves were each inoculated IV with a gut homogenate extracted from 50 adult ticks and monitored for patent A marginale infection. The prepatent periods were determined and used as a measure of infectivity. Gut homogenates made from ticks that had been incubated for 2.5 days produced infections with the shortest prepatent periods, an average of 28.5 days among 3 trials.

Infection of splenectomized calves with Anaplasma ovis

An Anaplasma was not recovered from 2 splenectomized calves at 17 days after A ovis inoculation, but was recovered from 1 of the calves at 177 days after inoculation. In a 3rd calf exposed to A ovis, an Anaplasma was recovered at 177 and 262 days after inoculation. the Anaplasma recovered from these calves was determined to be A ovis on the basis of cross-infectivity trials, using Anaplasma marginale.