Host surveys, ixodid tick biology and transmission scenarios as related to the tick-borne pathogen, Ehrlichia canis

Ticks and tick-borne diseases from Mallorca Island, Spain

Ixodid ticks are obligate blood-feeding arthropods and important vectors of pathogens. In Mallorca, almost no data on the tick fauna are available. Herein, we investigated ticks and tick-borne pathogens in ticks collected from dogs, a cat and humans in Mallorca as result of a citizen science project. A total of 91 ticks were received from German tourists and residents in Mallorca. Ticks were collected from March to October 2023 from dogs, cat and humans, morphologically and genetically identified and tested for pathogens by PCRs. Six tick species could be identified: Ixodes ricinus (n = 2), Ixodes ventalloi (n = 1), Hyalomma lusitanicum (n = 7), Hyalomma marginatum (n = 1), Rhipicephalus sanguineus s.l. (n = 71) and Rhipicephalus pusillus (n = 9). Rhipicephalus sanguineus s.l. adults were collected from dogs and four females from a cat and the 16S rDNA sequences identified it as Rh. sanguineus s.s. Hyalomma lusitanicum was collected from 1 human, 1 dog and 5 specimens were collected from the ground in the community of Santanyi, together with one H. marginatum male. This is the first report of Hyalomma marginatum in Mallorca. Both I. ricinus were collected from humans and I. ventalloi female was collected from a dog. All ticks tested negative for Anaplasma phagocytophilum, Coxiella spp., Francisella spp., and piroplasms. In 32/71 (45%) specimens of Rh. sanguineus s.s., Rickettsia spp. could be detected and in 18/32 (56.2%) sequenced tick DNAs R. massiliae was identified. Ixodes ventalloi female and both I. ricinus tested positive in the screening PCR, but the sequencing for the identification of the Rickettsia sp. failed.

Ehrlichia canis and Rickettsia conorii Infections in Shelter Dogs: Seropositivity and Implications for Public Health

A cross-sectional study was conducted to gain insight into the epidemiology of canine ehrlichiosis and rickettsiosis in northern Portugal. Specific IgG antibodies to Ehrlichia canis were analysed using a commercial enzyme-linked immunosorbent assay (ELISA), and antibodies to Rickettsia conorii were analysed using a commercial indirect immunofluorescence antibody test (IFAT). A total of 113 dogs from two different shelters were sampled, and seroprevalence values of 0.9% (95% confidence (CI): 0.2-4.8%) for E. canis and 9.7 (95% CI: 5.5-16.6%) for R. conorii were found. Multiple logistic regression investigated risk factors for seropositivity. The odds ratios (ORs) of R. conorii seropositivity were higher for female dogs (OR = 6.429; 95% CI: 1.201-34.407). Dogs seropositive for co-infection (E. canis + R. conorii) were more frequently observed among females (OR = 7.606; CI 95%: 1.478-39.132) and in Shelter 2 (OR = 18.229; 95% CI: 2.190-151.756). These findings show that shelter dogs in northern Portugal are exposed to E. canis and R. conorii, which can affect both canines and humans. It is imperative to adopt a One Health approach to educate the public about the hazards of canine zoonoses and develop legislation and procedures to control their spread and preserve public health.

Pleural effusion-related Nocardia otitidiscaviarum, Anaplasma platys and Ehrlichia canis coinfection in a dog

The coinfections by some microorganisms have been related to severe diseases in humans and animals, where immunosuppressive agents favor opportunistic behavior of other pathogens. A 4-month-old, female mixed-breed dog with a two-week history of inappetence, prostration, emaciation, and respiratory distress was admitted at a veterinary hospital in Brazil. Tachycardia, pale mucous membranes, severe respiratory distress, and a large number of ticks (Rhipicephalus sanguineus s.l.) in different body regions were observed at clinical examination. Hematological examination of dog showed leukocytosis, neutrophilia, mild anemia, and thrombocytopenia, whereas unremarkable values in biochemical tests. Thoracic radiography revealed a pleural effusion image. Blood and the pleural fluid (purulent aspect) samples were subjected to qPCR (16S rRNA and dsb genes) and sequencing, which identified Ehrlichia canis and Anaplasma platys coinfection. An aggregate of coccoid-to-branching or long filamentous microorganisms, surrounded by pyogranulomatous inflammatory reaction was seen at the cytology of the pleural fluid. Bacteriological culture of pleural effusion showed colonies compatible with the genus Nocardia, which revealed gram-positive filamentous organisms with a tendency of fragmentation and were identified as Nocardia otitidiscaviarum in mass spectrometry (MALDI-TOF MS). Therapy of N. otitidiscaviarum isolate using levofloxacin (supported by a previous in vitro susceptibility testing) and doxycycline for E. canis and A. platys resulted in complete resolution of the clinical picture. Here, we report for the first time a triple coinfection by Nocardia otitidiscaviarum, A. platys, and E. canis in a dog with pleural effusion, where debilitating or immunosuppressive conditions induced by A. platys and E. canis coinfection probably contributed to the opportunistic behavior of N. otitidiscaviarum.

Ehrlichia canis rapid spread and possible enzooty in northern South Australia and distribution of its vector Rhipicephalus linnaei

Recent concerns have arisen in Australia regarding detections of the exotic bacterium Ehrlichia canis which has resulted in ehrlichiosis outbreaks. In Australia, it is spread by the tropical brown dog tick Rhipicephalus linnaei, formerly Rhipicephalus sanguineus sensu lato tropical lineage. Previously, the tick has been recorded in South Australia in the Coober Pedy and the Oodnadatta areas. This study, which includes historical specimens data held in historical Australian arthropod collections, along with 10 sampled remote communities, confirms the wide distribution range of this species within the State. E. canis was detected by PCR in the ticks. The percentage of dogs hosting PCR-positive ticks increased from 2.8% (95% confidence interval [CI]: 0.3 to 9.7) in November-December 2020 to 62.9% (95% CI: 44.9 to 78.5) end of February 2021, initially in two then in seven Anangu Pitjantjatjara Yankunytjatjara lands communities in the far northern regions of South Australia. Our results suggest a rapid spread of the pathogen. No evidence of E. canis was found in nine regional communities. The extended tropical brown dog tick distribution indicates a greater area where E. canis may occur and may require management to minimise the impacts of ehrlichiosis outbreaks. Without the implementation of effective detection and control programs, this extended distribution of R. linnaei is likely to result in the spread of the bacterium to other regions.

Bacteria related to tick-borne pathogen assemblages in Ornithodoros cf. hasei (Acari: Argasidae) and blood of the wild mammal hosts in the Orinoquia region, Colombia

Interest in research on soft ticks has increased in recent decades, leading to valuable insight into their role as disease vectors. The use of metagenomics-based analyses have helped to elucidate ecological factors involved in pathogen, vector, and host dynamics. To understand the main bacterial assemblages present in Ornithodoros cf. hasei and its mammalian hosts, 84 ticks and 13 blood samples from bat hosts (Chiroptera) were selected, and the 16S rRNA gene V4 region was sequenced in five pools (each one related to each host-tick pairing). Bacterial taxonomic assignment analyses were performed by comparing operational taxonomic units (OTUs) shared between ticks and their host blood. This analysis showed the presence of Proteobacteria (38.8%), Enterobacteriaceae (25%), Firmicutes (12.3%), and Actinobacteria (10.9%) within blood samples, and Rickettsiaceae (39%), Firmicutes (25%), Actinobacteria (13.1%), and Proteobacteria (9%) within ticks. Species related to potentially pathogenic genera were detected in ticks, such as Borrelia sp., Bartonella tamiae, Ehrlichia sp. and Rickettsia-like endosymbiont, and the presence of these organisms was found in all analyzed bat species (Cynomops planirostris, Molossus pretiosus, Noctilio albiventris), and O. cf. hasei. About 41-48.6% of bacterial OTUs (genera and species) were shared between ticks and the blood of bat hosts. Targeted metagenomic screening techniques allowed the detection of tick-associated pathogens for O. cf. hasei and small mammals for the first time, enabling future research on many of these pathogens.

Invasive raccoon (Procyon lotor) and raccoon dog (Nyctereutes procyonoides) as potential reservoirs of tick-borne pathogens: data review from native and introduced areas

In recent decades, populations of the raccoon (Procyon lotor) and the raccoon dog (Nyctereutes procyonides) have increased and adapted to peri-urban and urban environments in many parts of the world. Their ability to rapidly colonize new territories, high plasticity and behavioral adaptation has enabled these two species to be considered two of the most successful invasive alien species. One of the major threats arising from continually growing and expanding populations is their relevant role in maintaining and transmitting various vector-borne pathogens among wildlife, domestic animals and humans. According to the WHO, over 17% of infectious diseases are vector-borne diseases, including those transmitted by ticks. Every year tick-borne pathogens (TBPs) create new public health challenges. Some of the emerging diseases, such as Lyme borreliosis, anaplasmosis, ehrlichiosis, babesiosis and rickettsiosis, have been described in recent years as posing important threats to global health. In this review we summarize current molecular and serological data on the occurrence, diversity and prevalence of some of the TBPs, namely Babesia, Theileria, Hepatozoon, Borrelia, Rickettsia, Bartonella, Anaplasma and Ehrlichia, that have been detected in raccoons and raccoon dogs that inhabit their native habitats and introduced areas. We draw attention to the limited data currently available on these invasive carnivores as potential reservoirs of TBPs in different parts of the world. Simultaneously we indicate the need for more research in order to better understand the epidemiology of these TBPs and to assess the future risk originating from wildlife.

Genetic variability of Ehrlichia canis TRP36 in ticks, dogs, and red foxes from Eurasia

Ehrlichia canis is among the most prevalent tick-borne pathogens infecting dogs worldwide, being primarily vectored by brown dog ticks, Rhipicephalus sanguineus sensu lato (s.l.). The genetic variability of E. canis has been assessed by analysis of different genes (e.g., disulfide bond formation protein gene, glycoprotein 19, tandem repeat protein 36 - TRP36) in the Americas, Africa, Asia, and in a single dog sample from Europe (i.e., Spain). This study was aimed to assess the variations in the TRP36 gene of E. canis detected in naturally infected canids and R. sanguineus s.l. ticks from different countries in Asia and Europe. DNA samples from dogs (n = 644), foxes (n = 146), and R. sanguineus s.l. ticks (n = 658) from Austria, Italy, Iran, Pakistan, India, Indonesia, Malaysia, the Philippines, Singapore, Thailand, Vietnam, and Taiwan were included in this study. Ehrlichia canis 16S rRNA positive samples (n = 115 from the previous studies; n = 14 from Austria in this study) were selected for molecular examination by analyses of TRP36 gene. Out of 129 E. canis 16S rRNA positive samples from dogs (n = 88), foxes (n = 7), and R. sanguineus s.l. ticks (n = 34), the TRP36 gene was successfully amplified from 52. The phylogenetic analysis of the TRP36 pre-repeat, tandem repeat, and post repeat regions showed that most samples were genetically close to the United States genogroup, whereas two samples from Austria and one from Pakistan clustered within the Taiwan genogroup. TRP36 sequences from all samples presented a high conserved nucleotide sequence in the tandem repeat region (from 6 to 20 copies), encoding for nine amino acids (i.e., TEDSVSAPA). Our results confirm the US genogroup as the most frequent group in dogs and ticks tested herein, whereas the Taiwan genogroup was present in a lower frequency. Besides, this study described for the first time the US genogroup in red foxes, thus revealing that these canids share identical strains with domestic dogs and R. sanguineus s.l. ticks.

Seroprevalence of Ehrlichia spp., Anaplasma spp., Borrelia burgdorferi sensu lato, and Dirofilaria immitis in Stray Dogs, from 2016 to 2019, in Southern Italy

Canine vector-borne diseases (CVBD) are an important and emerging health concern for humans and animals worldwide. The purpose of the presented study was to assess, from 2016 to 2019, the seroprevalence of CVBD agents and clarify the epidemiology of tick-borne disease in stray dogs living in the Campania Region, Southern Italy. For this purpose, blood samples were collected from January 2016 to December 2019 from 1023 dogs in authorized kennels located in the five municipalities of the Campania Region. SNAP^® 4DX^® from IDEXX^® Laboratories was used for detection of Ehrlichia spp., Anaplasma spp., Borrelia burgdorferi sensu lato (s.l.), and Dirofilaria immitis antibodies. The overall seroprevalence of CVBD in stray dogs was 19.6% (95% Confidence Intervals (CI): 17.2-22.8%; 201/1023). The most common pathogen was Ehrlichia spp., with a percentage of positivity of 16.03%, followed by Anaplasma spp. with 7.8%. B. burgdorferi s.l. and D. immitis were detected in only 0.2% of dogs; co-infection was detected in 4.5% of stray dogs tested. No link was detected between the gender, age, location, and CVBD seropositivity, except for Ehrlichia spp. for which location (Avellino Province; p = 0.007) and gender (male, p = 0.002) were risk factors for seropositivity. Our results demonstrated that animals are exposed to at least one of the four etiological agents (Ehrlichia spp., Anaplasma spp. Borrelia burgdorferi s.l., and Dirofilaria immitis) transmitted by vectors. Finally, this study highlighted the utility of serological monitoring in stray dogs, housed in kennels, given the threat posed by CVBD to animals and the zoonotic implications of these etiological agents and their vectors on human health.

Serological prevalence of six vector-borne pathogens in dogs presented for elective ovariohysterectomy or castration in the South central region of Texas

Background

Most vector-borne pathogens cause zoonotic diseases. These zoonoses often have wild animal reservoirs that play a significant role in disease epidemiology. However, pet animals have also been implicated in transmission of zoonotic agents to humans. To exemplify, dogs are competent reservoir hosts for several zoonotic vector-borne bacteria and protozoa. Despite that vector-borne diseases can be life-threatening for both pets and humans, studies on pathogen seroprevalence are very limited. Therefore, the objective of this study was to determine the serological prevalence of six zoonotic vector-borne agents in dogs from the South Central region of Texas (US).

Electronic medical records of dogs, presenting over 2014–2019 for elective ovariohysterectomy or castration at a high volume spay and neuter clinic, were reviewed for serological testing. Sera from 418 dogs were tested for the Dirofilaria immitis antigen, and antibodies to Anaplasma phagocytophilum, Anaplasma platys, Borrelia burgdorferi, Ehrlichia canis, and Ehrlichia ewingi, using a commonly available commercial test kit. Descriptive statistics were computed to characterize the respective seroprevalence rates of the dog population. The study involved 192 (46%) male and 226 (54%) female dogs.

Results

Overall, 85 (20%) dogs tested positive for at least one of the 6 pathogens investigated. The highest seroprevalence rate averaged over the 6-year period was 11.7% for D. immitis followed by 8.4% for E. canis and/or E. ewingii, 4.3% for A. phagocytophilum and/or A. platys, and 0.2% for B. burgdorferi. The co-exposure or co-infection was only detected in 3.8% of the dog population.

Conclusions

Together, opportunistic testing of dogs presenting for elective surgical procedures may provide an effective way of assessing seroprevalence and/or risk factors for common vector-borne diseases within a geographic region of concern.

Prevalence of antibodies against Anaplasma spp., Borrelia burgdorferi sensu lato, Babesia gibsoni, and Ehrlichia spp. in dogs in the Republic of Korea

There is a lack of comprehensive studies on the seroprevalence of tick-borne pathogens in the Republic of Korea. Therefore, the aim of this study was to investigate the seroprevalences of Anaplasma spp. (A. phagocytophilum/A. platys), Borrelia burgdorferi sensu lato, Babesia gibsoni, Ehrlichia spp. (E. canis/E. ewingii), and Ehrlichia chaffeensis in dogs across the Republic of Korea in 2017 and 2018. A total of 2215 serum samples collected from 938 companion dogs, 969 shelter dogs, and 308 military working dogs were examined using commercial enzyme-linked immunosorbent assay (ELISA) and indirect fluorescence immunoassay (IFA) kits. Data collected for each animal, including breed, sex, age, region, season, and dog type, were used for statistical analysis. The overall seroprevalence was highest for Anaplasma spp. (15.1 %), followed by Ehrlichia spp. (10.3 %), B. burgdorferi sensu lato (6.4 %), E. chaffeensis (2.3 %), and B. gibsoni (1.7 %). One hundred and sixty-one dogs had antibodies against two or three different pathogens. The most common combinations were Anaplasma spp. - Ehrlichia spp. (2.1 %), Anaplasma spp. - E. chaffeensis (1.4 %), and Anaplasma spp. - B. burgdorferi sensu lato (1.2 %). Season was significantly associated with the seroprevalences of B. burgdorferi sensu lato and Ehrlichia spp., with dogs presenting the highest percentage of positive results during summer. Anaplasma spp. and B. gibsoni were significantly more prevalent in the northern and southern regions, respectively. The seroprevalences of Anaplasma spp., B. burgdorferi sensu lato, and Ehrlichia spp. were significantly higher in military working dogs, while the seroprevalence of E. chaffeensis was higher in companion dogs. The current findings are important for future surveillance of canine tick-borne pathogens and designing appropriate approaches for the diagnosis and control of these pathogens in the Republic of Korea.

Tick-borne pathogens in Ixodidae ticks collected from privately-owned dogs in Italy: a country-wide molecular survey

Background

Ticks and tick-borne diseases are increasingly recognized as a cause of disease in dogs worldwide. The epidemiology of ticks and tick-transmitted protozoa and bacteria has changed due to the spread of ticks to urban and peri-urban areas and the movement of infected animals, posing new risks for animals and humans. This countrywide study reports information on distribution and prevalence of pathogens in ticks collected from privately-owned dogs in Italy.

We analyzed 2681 Ixodidae ticks, collected from 1454 pet dogs from Italy. Specific PCR protocols were used to detect i) Piroplasms of the genera Babesia and Theileria, ii) Gram-negative cocci of the family Anaplasmataceae and iii) Borrelia burgdorferi sensu lato. Sequencing of positive amplicons allowed for species identification.

Results

Babesia/Theileria spp. DNA was detected in 435 homogeneous tick-pools (Minimum Infection Rate (MIR) = 27.6%; 95% confidence interval (CI) = 25.4–29.8%) with higher prevalence in Ixodes ricinus and Rhipicephalus sanguneus group. The zoonotic B. venatorum was the most prevalent species (MIR = 7.5%; 95% CI = 6.3–9.0%). Anaplasma and Ehrlichia species were detected in 165 tick-pools (MIR = 10.5%; 95% CI = 9.3–11.8%) and specifically, A. phagocytophilum was identified with MIR = 5.1% (95% CI = 4.1–6.3%). Borrelia burgdorferi s.l. and B. afzelii were detected with MIR = 0.4% (95% CI = 0.2–0.8%) and MIR = 0.3% (95% CI 0.1–0.7%) respectively.

Conclusions

Zoonotic pathogens B. venatorum and A. phagocytophilum were the most frequently detected in ticks collected from privately-owned dogs which might be used as markers of pathogens presence and distribution.

Anti-Ehrlichia properties of the essential oil of Ageratum conyzoides L. and its interaction with doxycycline

Canine Monocytic Ehrlichiosis (CME) is an infectious disease caused by the rickettsia organism Ehrlichia canis which is transmitted mainly the ixodid brown dog tick Rhipicephalus sanguineus. The prevalence of E. canis infection has been increasing in recent years. The World Health Organization has been warned about antibiotics resistance and one of the way to prevent this situation is found new compound with this property. Doxycycline is the treatment of choice for this tick-borne disease. Adverse effects are noted in dogs that are sensitive to this drug. Antibiotic resistance may also occur. The present study aimed to evaluate the anti-Ehrlichia properties of the essential oil of the aerial parts of Ageratum conyzoides L. in infected DH82 cells, as well as its anti-Ehrlichia activity associated with doxycycline using the checkerboard assay. A. conyzoides is a native plant from northeast Brazil with many reports of ethnopharmacological applications. The essential oil of A. conyzoides was extracted from the aerial parts of the plant using the hydrodistillation method. E. canis-infected DH82 cells were cultured in DMEM (Dulbecco’s Modified Eagle Medium), maintained at 37 °C and 5% CO₂, and standardized at a 70% infection rate for the initiation of treatment protocols. The tests were first carried out with the aim of defining the IC₅₀. The combined effect of doxycycline and A. conyzoides essential oil was then determined using the checkerboard dilution technique (checkerboard method) in which the IC₅₀ was 200 µg/mL. The doxycycline reduction index from the combined effect was 4.90 times resulting in a synergistic effect. To the authors’ knowledge, this is the first alternative treatment (alternative therapy) based on bioactive molecules that have antibacterial activity against E. canis.

Diversity of Anaplasma and Ehrlichia/Neoehrlichia Agents in Terrestrial Wild Carnivores Worldwide: Implications for Human and Domestic Animal Health and Wildlife Conservation

Recently, the incidence and awareness of tick-borne diseases in humans and animals have increased due to several factors, which in association favor the chances of contact among wild animals and their ectoparasites, domestic animals and humans. Wild and domestic carnivores are considered the primary source of tick-borne zoonotic agents to humans. Among emergent tick-borne pathogens, agents belonging to family Anaplasmataceae (Order Rickettsiales) agents stand out due their worldwide distribution and zoonotic potential. In this review we aimed to review the genetic diversity of the tick-transmitted genera Ehrlichia, Anaplasma and "Candidatus Neoehrlichia sp." in wild carnivores Caniformia (Canidae, Mustelidae and Ursidae) and Feliformia (Felidae, Hyanidae, Procyonidae and Viverridae) worldwide, discussing the implications for human and domestic animal health and wildlife conservation. Red foxes (Vulpes vulpes) have been identified as hosts for Anaplasma spp. (A. phagocytophilum, Anaplasma ovis, A. platys), Ehrlichia canis and "Candidatus Neoehrlichia sp." (FU98 strain) and may contribute to the maintaenance of A. phagocytophilum in Europe. Raccoons (Procyon lotor) have been reported as hosts for E. canis, A. bovis, "Candidatus Neoehrlichia lotoris" and A. phagocytophilum, and play a role in the maintenance of A. phagocytophilum in the USA. Raccoon dogs (Nyctereutes procyonoides) may play a role as hosts for A. bovis and A. phagocytophilum. New Ehrlichia and/or Anaplasma genotypes circulate in wild canids and felids from South America and Africa. While Ehrlichia sp. closely related to E. canis has been reported in wild felids from Brazil and Japan, Anaplasma sp. closely related to A. phagocytophilum has been detected in wild felids from Brazil and Africa. Red foxes and mustelids (otters) are exposed to E. canis in countries located in the Mediaterranean basin, probably as a consequence of spillover from domestic dogs. Similarly, E. canis occurs in procyonids in North (raccoons in USA, Spain) and South (Nasua nasua in Brazil) Hemispheres, in areas where E. canis is frequent in dogs. While "Candidatus Neoehrlichia lotoris" seems to be a common and specific agent of raccoons in the USA, "Candidatus Neoehrlichia sp." (FU98 strain) seems to show a broader range of hosts, since it has been detected in red fox, golden jackal (Canis aureus) and badger (Meles meles) in Europe so far. Brown (Ursus arctos) and black (Ursus americanus) bears seem to play a role as hosts for A. phagocytophilum in the North Hemisphere. Anaplasma bovis has been detected in wild Procyonidae, Canidae and Felidae in Asia and Brazil. In order to assess the real identity of the involved agents, future works should benefit from the application of MLST (Multi Locus Sequence Typing), WGS (Whole Genome Sequencing) and NGS (Next Generation Sequencing) technologies aiming at shedding some light on the role of wild carnivores in the epidemiology of Anaplasmataceae agents.

Detection of tick-borne pathogens in ticks from dogs and cats in different European countries

Ticks are known to transmit pathogens which threaten the health and welfare of companion animals and man globally. In the present study, mainly adult ticks were collected from dogs and cats presented at their local veterinary practice in Hungary, France, Italy, Belgium (dogs only) and Germany (cats only), and identified based on tick morphology. If more than one tick was collected from a host animal, ticks were pooled by tick species for DNA extraction and subsequent PCR examination for the presence of tick-borne pathogens. Out of 448 tick samples, 247 (95 from dogs and 152 from cats) were Ixodes ricinus, 26 (12 from dogs and 14 from cats) were I. hexagonus, 59 (43 from dogs and 16 from cats) were Dermacentor reticulatus and 116 (74 from dogs and 42 from cats) were Rhipicephalus sanguineus sensu lato (s.l.). In 17% of the I. ricinus samples Anaplasma phagocytophilum was found. Borrelia spp. were mainly identified in I. ricinus collected from cats (18%) and to a lesser extent in dog-sourced ticks (1%), with Borrelia afzelii (n = 11), B. garinii (n = 7), B. valaisiana (n = 5), B. lusitaniae (n = 3) and B. burgdorferi sensu stricto (n = 3) being identified. One I. hexagonus sample collected from a cat in France tested positive for B. afzelii. Babesia canis was detected in 20% of the D. reticulatus samples, mainly from Hungary. Rhipicephalus sanguineus s.l. was found positive for Hepatozoon canis (3%), A. platys (5%) and three Rickettsia species (7%; R. massiliae; R. raoultii and R. rhipicephali). Furthermore, a total of 66 R. sanguineus s.l. ticks were subjected to molecular analysis and were identified as R. sanguineus sp. II-temperate lineage, with seven haplotypes recorded. Amongst them, the most prevalent sequence types were haplotype XIII (n = 24; 69%) and haplotype XIV (n = 16; 52%) in France and in Italy, respectively, found both in cats and dogs. Although differences related to both country and host, were observed, the results of this study indicate that cats and dogs are exposed to tick-borne pathogen infected ticks, which may represent a medical risk to these host animals.

Molecular Evidence for Transstadial Transmission of Ehrlichia canis by Rhipicephalus sanguineus sensu lato Under Field Conditions

This study investigated possible transstadial transmission of Ehrlichia canis by Rhipicephalus sanguineus sensu lato collected from shelter dogs and the shelter grounds in Diyarbakır Province of south-eastern Turkey. Totally 225 engorged nymphs were collected from eight infected dogs with E. canis and incubated at 28°C for moulting. Unfed ticks from the shelter grounds comprising 1,800 larvae, 3,100 nymphs, and 85 adults were sorted according to sampling origin, life stage, and sex into 116 pools and screened by 16S rRNA PCR. Nine out of 26 pools of unfed adult ticks were positive for E. canis, with overall infection rate maximum likelihood estimation (MLE) of 4.83 (CI 2.39-8.87). E. canis was detected in three of 12 male pools (MLE 3.22, CI 0.86-8.83) and six of 14 female pools (MLE 6.16, CI 2.59-12.90). No adult pools collected from the shelter grounds were positive. Among 62 unfed nymph pools collected from the shelter, six were infected with E. canis (MLE 0.20, CI 0.08-0.42). No E. canis DNA was detected in any of the larva pools. Our results revealed molecular evidence for transstadial transmission of E. canis by R. sanguineus s.l. both from larva to nymph and from nymph to adult. We found no evidence of transovarial transmission.

Arthropod-borne pathogens of dogs and cats: From pathways and times of transmission to disease control

Vector-borne pathogens have developed a close relationship with blood feeding arthropod ectoparasites (e.g., mosquitoes, ticks, phlebotomine sand flies, black flies, fleas, kissing bugs, lice) and exploited a huge variety of vector transmission routes. Therefore, the life cycles of these pathogens result in a long evolved balance with the respective arthropod biology, ecology and blood feeding habits, instrumentally to the infection of several animal species, including humans. Amongst the many parasite transmission modes, such as ingestion of the arthropod, with its faeces or secretions, blood feeding represents the main focus for this article, as it is a central event to the life of almost all arthropod vectors. The time frame in which pathogens are transmitted to any animal host is governed by a large number of biological variables related to the vector, the pathogen, the host and environmental factors. Scientific data available on transmission times for each pathogen are discussed relative to their impact for the success of vector-borne disease control strategies. Blocking pathogen transmission, and thus preventing the infection of dogs and cats, may be achievable by the use of chemical compounds if they are characterised by a fast onset of killing activity or repellence against arthropods. The fast speed of kill exerted by systemic isoxazoline, as well as the repellent effect of pyrethroids have renewed the interest of the scientific community and pharmaceutical companies towards reducing the burden of vector-borne diseases under field conditions. However, endosymbionts and vaccines targeting arthropods or pathogen antigens should be further investigated as alternative strategies towards the goal of achieving an effective integrated control of vector-borne diseases.

Blocking transmission of vector-borne diseases

Vector-borne diseases are responsible for significant health problems in humans, as well as in companion and farm animals. Killing the vectors with ectoparasitic drugs before they have the opportunity to pass on their pathogens could be the ideal way to prevent vector borne diseases. Blocking of transmission might work when transmission is delayed during blood meal, as often happens in ticks. The recently described systemic isoxazolines have been shown to successfully prevent disease transmission under conditions of delayed pathogen transfer. However, if the pathogen is transmitted immediately at bite as it is the case with most insects, blocking transmission becomes only possible if ectoparasiticides prevent the vector from landing on or, at least, from biting the host. Chemical entities exhibiting repellent activity in addition to fast killing, like pyrethroids, could prevent pathogen transmission even in cases of immediate transfer. Successful blocking depends on effective action in the context of the extremely diverse life-cycles of vectors and vector-borne pathogens of medical and veterinary importance which are summarized in this review. This complexity leads to important parameters to consider for ectoparasiticide research and when considering the ideal drug profile for preventing disease transmission.

The Eurasian otter (Lutra lutra) as a potential host for rickettsial pathogens in southern Italy

Canine monocytic ehrlichiosis and rickettsiosis are zoonotic tick-borne diseases of canids caused by the intracellular obligate bacteria Ehrlichia canis and Rickettsia species respectively. In this study, we investigated using standard and real-time PCR and sequencing, the occurrence and molecular characterization of E. canis and Rickettsia species in the Eurasian otter (Lutra lutra) from the southern Italian population. Samples were screened by using molecular assays also for Neospora caninum, Toxoplasma gondii, Clamydophyla spp., Coxiella burnetii, Leishmania spp., Cryptosporidium spp., and Giardia spp. detection, and helminths were studied by traditional methods. Out of six carcasses tested, three were positive for E. canis and co-infection with Rickettsia sp. occurred in one of those. Sequences of the 16S rRNA E. canis gene were identical to each other but differed from most of those previously found in red foxes (Vulpes vulpes) and wolves (Canis lupus) from southern Italy. Helminths included just cystacanths of Sphaerirostris spp. from the intestine of two Eurasian otters and the nematode Angiostrongylus vasorum from the lungs of a single Eurasian otter. None of the samples was positive for the other investigated selected pathogens. This study is the first report on the evidence of infection by rickettsial pathogens in the Eurasian otter. The present result prompts some inquiries into the pathogenic role of those bacteria for the isolated sub-populations of the endangered Eurasian otter in southern Italy.

HEMATOLOGICAL PARAMETERS AND SEROPREVALENCE OF Ehrlichia canis AND Babesia vogeli IN DOGS

Abstract The aim of this study was to determine the prevalence of anti-Ehrlichia canis and anti-Babesia vogeli IgG antibodies in dogs and correlate this prevalence with risk factors to evaluate the relation of serological status to hematological findings. Blood samples of dogs attended from September 2011 to March 2012 at the veterinary hospital of the Federal University of Lavras, Brazil, were analyzed using an indirect fluorescence antibody test (IFAT). Of the total 160 dog serum samples, 23.7% (38 dogs; CI95 17.7% - 30.7%) were seropositive for E. canis, 40.0% (64 dogs; CI95 40.0% - 59.2%) for B. vogeli, and 5.6% (9 dogs) for both hemoparasites. None of the epidemiological variables showed a significant association (P>0.05) with seropositivity to E. canis and B. vogeli. Dogs seropositive for E. canis showed lower values for hematocrit (P<0.05). However, for the erythrogram, the platelet count, the leukogram and clinical signs, no significant difference (P>0.05) was observed between dogs that were seropositive and seronegative for E. canis or for B. vogeli. Serological results suggest that infection with E. canis and B. vogeli is endemic in the canine population in question, with a prevalence of the subclinical phase (asymptomatic) in dogs that are seropositive for ehrlichiosis or babesiosis.

Associated Factors to Seroprevalence of Ehrlichia spp. in Dogs of Quintana Roo, Mexico

The objective of this study was to determine the seroprevalence to Ehrlichia spp. in dogs from Xcalak, Quintana Roo, Mexico, and the associated factors. Serum samples were obtained from 118 dogs and used in an indirect immunofluorescent assay test for the detection of antibodies against Ehrlichia spp. A questionnaire was used to obtain information about possible variables associated with seroprevalence. These variables were analyzed through Chi² test and logistic regression. Dog seroprevalence of antibodies against Ehrlichia spp. was 64% (75/118). Fifty-two percent (61/118) of dogs had tick infestation which was identified as Rhipicephalus sanguineus sensu lato. Anemia was observed in 36% of dogs. Leucopenia (2.5%), thrombocytopenia (70%), and hemorrhage (14%) were also observed. Thirty-one percent (23/75) of dogs with anemia, 4% (3/75) of dogs with leucopenia, 80% (60/75) of dogs with thrombocytopenia, 17% (13/75) of dogs with hemorrhages, and 59% (44/75) of dogs with ticks were positive for Ehrlichia spp. antibodies. The factors associated with seroprevalence were age (1–3 and >3 years old, OR = 7.77 and OR = 15.39, resp.), tick infestation (OR = 3.13), and thrombocytopenia (OR = 3.36). In conclusion, seroprevalence of Ehrlichia spp. was high in the community of Xcalak and its associated factors were age, tick infestation, and thrombocytopenia.

Countrywide serological evaluation of canine prevalence for Anaplasma spp., Borrelia burgdorferi (sensu lato), Dirofilaria immitis and Ehrlichia canis in Mexico

BACKGROUND

Canine vector-borne diseases (CVBD) have become a major concern for canine and human public health. The aim of the study described here is to add epidemiological data regarding four pathogens responsible for CVBD, namely anaplasmosis, borreliosis, dirofilariosis and ehrlichiosis in a national survey conducted in Mexico.

METHODS

Seventy-four veterinary centres located in 21 federal Mexican states were asked to test dogs with clinical signs suspect for CVBD and healthy dogs, for detection of Dirofilaria immitis antigen and antibodies against Anaplasma spp., Borrelia burgdorferi (sensu lato) and Ehrlichia canis using the SNAP® 4DX® from IDEXX® Laboratories.

RESULTS

A total of 1706 dogs were tested, including 943 apparently healthy and 722 CVBD-suspect dogs. Infected dogs were 36.7 %. The highest percentages of infection with E. canis (51.0 %) and Anaplasma spp. (16.4 %) were obtained in the northwestern region, while D. immitis was most frequently found in the northeastern region of the country (8.9 %). Four dogs from the northwestern, northeastern, eastern and southeastern regions, respectively, were positive for B. burgdorferi (sensu lato). Northcentral regions showed lowest overall prevalence of infection (2.4 %). Co-infections were detected in 8.8 % of the dogs tested. Statistically significant lower positivity was found among dogs aged less than one year (23.2 %) and small-sized dogs (27.6 %), while higher prevalence of infection was found in dogs living outdoors (42.0 %), dogs with detectable tick infestation (43.3 %) and dogs that received treatment for tick-transmitted infections (58.8 %). Seropositivity was a risk factor for the presence of clinical signs as follows: Anaplasma spp. (OR = 2.63; 95 % CI: 1.88-3.67; P < 0.0001), D. immitis (OR = 2.52; 95 % CI: 1.61-3.95; P < 0.0001), E. canis (OR = 3.58; 95 % CI: 2.88-4.45; P < 0.0001), mixed infections (OR = 4.08; 95 % CI: 2.79-5.96; P < 0.0001), one or more agents (OR = 3.58; 95 % CI: 2.91-4.42; P < 0.0001).

CONCLUSIONS

Canine serological evidence supports that dogs from Mexico are at risk of acquiring Anaplasma spp., D. immitis and/or E. canis, while B. burgdorferi (sensu lato) transmission is minimal in the country. Practitioners play a fundamental role in the detection and control of these diseases to protect dogs and humans.

Molecular survey of canine vector-borne diseases in stray dogs in Thailand

Despite the large population of stray dogs in Thailand, there is limited information on the prevalence of canine vector-borne diseases (CVBDs). In this study, a molecular survey was conducted to determine the prevalence of Babesia spp., Ehrlichia canis, Hepatozoon spp., Anaplasma platys and Mycoplasma spp. in dogs in Thailand. Of the 181 dog blood samples tested by PCR, 78/181 (43.1%) were found to be infected with one or more pathogens. The overall prevalence rates of Mycoplasma spp., Hepatozoon spp., Babesia spp., A. platys and E. canis infections were 19.9%, 18.8%, 9.4%, 4.4% and 3.9%, respectively. To the authors' knowledge, this is the first report of Mycoplasma infection in Thailand in dogs. The current findings are important for future surveillance of CVBDs and designing appropriate approaches for diagnosis and control for the diseases in Thailand.

Molecular detection of vector-borne pathogens in wild and domestic carnivores and their ticks at the human-wildlife interface

Urbanization of natural areas is considered one of the causes of the current apparent emergence of infectious diseases. Carnivores are among the species that adapt well to urban and periurban environments, facilitating cross-species disease transmission with domestic dogs and cats, and potentially with their owners. The prevalence of vector-borne pathogens (VBP) of zoonotic and veterinary interest was studied in sympatric wild and domestic carnivores into Barcelona Metropolitan Area (NE Spain). Blood or spleen samples from 130 animals, including 34 common genets (Genetta genetta), 12 red foxes (Vulpes vulpes), 10 stone martens (Martes foina), three Eurasian badgers (Meles meles), 34 free-roaming domestic cats and 37 dogs with outdoor access, were collected either in protected or adjacent residential areas. A total of 309 ticks (chiefly Rhipicephalus turanicus) were collected on these animals. The samples were analyzed with a battery of PCR assays targeting the DNA of Rickettsia spp., Anaplasmataceae, Coxiella burnetii, Bartonella spp., and Piroplasmida, and the amplicons were sequenced. The fox showed the highest prevalence (58%) and diversity of VBP (four pathogens), whereas none of the dogs were infected. Bartonella spp. (including B. clarridgeiae, B. henselae, and B. rochalimae) was the most prevalent pathogen. Infection of wild carnivores with Ehrlichia canis, C. burnetii, Theileria annae and Babesia vogeli was also confirmed, with some cases of coinfection observed. The presence of DNA of T. annae and B. vogeli was also confirmed in tick pools from four species of wild carnivores, supporting their role in piroplasmid life-cycle. By the sequencing of several target genes, DNA of Rickettsia massiliae was confirmed in 17 pools of Rh. turanicus, Rh. sanguineous, and Rh. pusillus from five different species, and Rickettsia conorii in one pool of Rh. sanguineous from a dog. None of the hosts from which these ticks were collected was infected by Rickettsia. Although carnivores may not be reservoir hosts for zoonotic Rickettsia, they can have an important role as mechanical dispersers of infected ticks.

Molecular detection of Anaplasma platys and Ehrlichia canis in dogs from Kabylie, Algeria

Ehrlichia canis and Anaplasma platys are bacteria belonging to the Anaplasmataceae family that cause acute, self-limiting and sometimes fatal vector-borne infections in dogs. These bacteria have been reported worldwide and are transmitted mainly by Rhipicephalus sanguineus. Aside from a report on E. canis once in 1935, no other Anaplasmataceae bacteria have been reported in Algeria to date. The aim of this study was to identify the microbial species implicated in ehrlichiosis and anaplasmosis by a molecular epidemiological survey in dogs. The study was carried out in Kabylie, in northeast Algeria. Sampling was performed in 11 municipalities in the province of Tizi Ouzou and 2 municipalities in the province of Béjaïa. Peripheral blood samples from 110 dogs were screened by qPCR, which is capable of identifying most Anaplasmataceae bacteria. Out of 110, a total of 13 samples screened positive (7/110 E. canis and 6/110 A. platys), and two genetic variants of A. platys and one of E. canis were identified. This is the first study to report the presence of A. platys in dogs from Algeria using a molecular investigative method. This survey was conducted in early spring. As tick activity can affect the prevalence of these pathogens in dogs, further investigations are needed to establish the year-round prevalence of these infections.

Molecular Diagnosis of Ehrlichia canis in Dogs and Ticks Rhipicephalus sanguineus (Acari: Ixodidae) in Yucatan, Mexico

Ehrlichia canis is the etiological agent behind canine monocytic ehrlichiosis, and the tick Rhipicephalus sanguineus (Latreille) is its main vector. Blood smear and nested polymerase chain reaction (PCR) techniques were used to identify E. canis infection in dogs and R. sanguineus, and explore factors possibly associated with infection in dogs in Yucatan, Mexico. Blood samples were taken and ticks R. sanguineus collected from 50 dogs (10 house dogs and 40 in an animal control center). Data were collected on dog age, sex, body condition, and signs associated with platelet deficiencies (epistaxis). Blood smears were analyzed to identify E. canis morulae and generate platelet counts. Nested PCR analysis was done on blood samples and 200 ticks. A χ(2) test was done to identify factors associated with the E. canis infection in the tested dogs. The overall prevalence for infection, as determined by PCR, was 36% (18 out of 50). All positive dogs were from samples collected from the animal shelter, representing prevalence, for this sampling site, of 45% (18 out of 40). Morulae in monocytes were identified in only 4% of samples. Dog origin (i.e. animal control center) was the only variable associated with E. canis infection (P < 0.01). Male ticks had a higher (P < 0.05) infection rate than female ticks (24.5 vs 13.5%). It is concluded that E. canis infection is present in both dogs and the brown dog ticks R. sanguineus in Yucatan, Mexico.

Birds as potential reservoirs of tick-borne pathogens: first evidence of bacteraemia with Rickettsia helvetica

Background

Birds have long been known as carriers of ticks, but data from the literature are lacking on their role as a reservoir in the epidemiology of certain tick-borne disease-causing agents. Therefore, the aim of this study was to evaluate the presence of three emerging, zoonotic tick-borne pathogens in blood samples and ticks of birds and to assess the impact of feeding location preference and migration distance of bird species on their tick infestation.

Methods

Blood samples and ticks of birds were analysed with TaqMan real-time PCRs and conventional PCR followed by sequencing.

Results

During the spring and autumn bird migrations, 128 blood samples and 140 ticks (Ixodes ricinus, Haemaphysalis concinna and a Hyalomma specimen) were collected from birds belonging to 16 species. The prevalence of tick infestation and the presence of tick species were related to the feeding and migration habits of avian hosts. Birds were shown to be bacteraemic with Rickettsia helvetica and Anaplasma phagocytophilum, but not with Candidatus Neoehrlichia mikurensis. The prevalence of rickettsiae was high (51.4%) in ticks, suggesting that some of them may have acquired their infection from their avian host.

Conclusion

Based on the present results birds are potential reservoirs of both I. ricinus transmitted zoonotic pathogens, R. helvetica and A. phagocytophilum, but their epidemiological role appears to be less important concerning the latter, at least in Central Europe.

Seropositivity rates for agents of canine vector-borne diseases in Spain: a multicentre study

Background

Controlling canine vector-borne diseases (CVBD) is a major concern, since some of these diseases are serious zoonoses. This study was designed to determine seropositivity rates in Spain for agents causing the following five CVBD: leishmaniosis (Leishmania infantum: Li), heartworm (Dirofilaria immitis: Di), ehrlichiosis (Ehrlichia canis: Ec), anaplasmosis (Anaplasma phagocytophilum/Anaplasma platys: An) and Lyme disease (Borrelia burgdorferi: Bb).

Methods

Anti-An, -Bb, and -Ec antibodies and the Di antigen were determined using the 4DX SNAP® Test (IDEXX Laboratories) and anti-L. infantum (Li) antibodies using the Leishmania SNAP® Test (IDEXX Laboratories) in blood and/or serum samples.

Results

Among 1100 dogs examined, overall seropositivity rates were: Li (15.7%), Ec (5%), An (3.1%), Di (1.25%) and Bb (0.4%). While seropositivity towards Bb and Di was similar in all geographic regions, rates were significantly higher in the east of Spain (8.3%) for An, significantly higher in the north (20%) for Ec, and significantly higher in the Southeast (46.6%) and South (27.4%), and significantly lower in the north (0%) for Li.

No statistical associations were observed between sex and the CVBD analyzed (p ≥ 0.05) while the following associations with other variables were detected: a higher seropositivity to Ec (40%) and Bb (6.7%) in dogs under one year of age compared with adults (p < 0.05); and a higher seropositivity to An and Li in dogs that lived outdoors versus indoors (p = 0.01; p < 0.001, respectively). Seropositivity rates of 2.1%, 0%, 1.7%, 0.5% and 4.2% were recorded respectively for An, Bb, Ec, Di and Li in dogs with no clinical signs (n = 556) versus 3.8%, 0.6%, 7.5%, 1.8% and 25.9% for those with signs (n = 507) suggestive of a CVBD.

Conclusion

The data obtained indicate a risk for dogs in Spain of acquiring any of the five CVBD examined. Veterinarians in the different regions should include these diseases in their differential diagnoses and recommend the use of repellents and other prophylactic measures to prevent disease transmission by arthropod vectors. Public health authorities also need to become more involved in the problem, since some of the CVBD examined here also affect humans.

Molecular evidence of Ehrlichia canis and Rickettsia massiliae in ixodid ticks of carnivores from South Hungary

To monitor the emergence of thermophilic, Mediterranean ixodid tick species and tick-borne pathogens in southern Hungary, 348 ticks were collected from shepherd dogs, red foxes and golden jackals during the summer of 2011. Golden jackals shared tick species with both the dog and the red fox in the region. Dermacentor nymphs were collected exclusively from dogs, and the sequence identification of these ticks indicated that dogs are preferred hosts of both D. reticulatus and D. marginatus nymphs, unlike previously reported. Subadults of three ixodid species were selected for reverse line blot hybridisation (RLB) analysis to screen their vector potential for 40 pathogens/groups. Results were negative for Anaplasma, Babesia and Theileria spp. Investigation of D. marginatus nymphs revealed the presence of Ehrlichia canis, Rickettsia massiliae and Borrelia afzelii for the first time in this tick species. These findings broaden the range of those tick-borne agents, which are typically transmitted by Rhipicephalus sanguineus, but may also have Dermacentor spp. as potential or alternative vectors. Ehrlichiacanis was also newly detected in Ixodes canisuga larvae from red foxes. In absence of transovarial transmission in ticks this implies that Eurasian red foxes may play a reservoir role in the epidemiology of canine ehrlichiosis.

Connection of toxin-antitoxin modules to inoculation eschar and arthropod vertical transmission in Rickettsiales

The biological role of toxin-antitoxin systems (TAS) in pathogenicity and cell addiction of Rickettsia was recently reported. We realized a comparative genomic analysis onto 33 rickettsial genomes and correlated the presence of TAS encoding genes with vertical transmission (VT) in arthropod hosts, the presence of inoculation eschar in humans and experimental animals, and the mortality in humans. There is a significant statistical link between TAS and the presence of an eschar (p≤0.0001). The presence of TAS is also significantly inversely correlated with mortality. The toxic effect of TAS may increase the local reaction, thus inhibiting the spread of rickettsiae associated with fatal outcome of the disease. The TAS were also linked to VT (p≤0.0001). Together with our previous findings we speculate that this is the first addiction system evidenced in intracellular bacteria. Thus, the TAS, as selfish genetic elements, might be essential to the evolutionary strategy of intracellular bacteria.

First detection and molecular characterization of Ehrlichia canis from dogs in Nigeria

The present study aimed to detect the presence of Ehrlichia canis in naturally infected dogs in Nigeria, using a combination of PCR and sequence analysis of the 16S rRNA gene and two genes encoding the tandem repeat-containing proteins (TRPs), TRP19 and TRP36. Out of a total of 100 blood samples collected from domestic dogs presented to veterinary hospitals in Jos, the capital city of Plateau State of Nigeria, 11 were positive in nested PCR for E. canis. Sequencing results for these amplicons showed that all of the 16S rDNA sequences (1623 bp) or the TRP19 coding sequences (414 bp) were identical to each other and had very high similarities (99.3-100%) with those from other E. canis strains accessible in GenBank. The TRP36 gene sequences derived from the 11 Nigerian isolates were identical to each other except for the number of the 27-bp repeat unit in a tandem repeat region, which was found to be 8, 12 or 18. Without considering the number of tandem repeats, these sequences had 100% identity to that of the reported Cameroon 71 isolate, but distinctly differed from those obtained from other geographically distant E. canis strains previously published. A phylogenetic tree of E. canis based on the TRP36 amino acid sequences showed that the Nigerian isolates and the Cameroon 71 isolate fell into a separate clade, indicating that they may share a common ancestor. Overall, this study not only provides the first molecular evidence of E. canis infections in dogs from Nigeria but also highlights the value of the TRP36 gene as a tool to classify E. canis isolates and to elucidate their phylogeographic relationships.

Contact with domestic dogs increases pathogen exposure in endangered African wild dogs (Lycaon pictus)

BACKGROUND

Infectious diseases have contributed to the decline and local extinction of several wildlife species, including African wild dogs (Lycaon pictus). Mitigating such disease threats is challenging, partly because uncertainty about disease dynamics makes it difficult to identify the best management approaches. Serious impacts on susceptible populations most frequently occur when generalist pathogens are maintained within populations of abundant (often domestic) "reservoir" hosts, and spill over into less abundant host species. If this is the case, disease control directed at the reservoir host might be most appropriate. However, pathogen transmission within threatened host populations may also be important, and may not be controllable by managing another host species.

METHODOLOGY/PRINCIPAL FINDINGS

We investigated interspecific and intraspecific transmission routes, by comparing African wild dogs' exposure to six canine pathogens with behavioural measures of their opportunities for contact with domestic dogs and with other wild dogs. Domestic dog contact was associated with exposure to canine parvovirus, Ehrlichia canis, Neospora caninum and perhaps rabies virus, but not with exposure to canine distemper virus or canine coronavirus. Contact with other wild dogs appeared not to increase the risk of exposure to any of the pathogens.

CONCLUSIONS/SIGNIFICANCE

These findings, combined with other data, suggest that management directed at domestic dogs might help to protect wild dog populations from rabies virus, but not from canine distemper virus. However, further analyses are needed to determine the management approaches--including no intervention--which are most appropriate for each pathogen.

Ehrlichiosis and anaplasmosis in dogs and cats

In the time since canine ehrlichiosis due to Ehrlichia canis was first described in 1935 and first recognized in the United States in 1962, many key advances have been made in our understanding of the diversity of the rickettsial organisms responsible for ehrlichiosis and anaplasmosis in dogs and, occasionally, cats, the vectors capable of transmitting these agents, and the role these organisms play as both important veterinary pathogens and zoonotic disease agents. Despite considerable progress in the field, much remains to be learned regarding mechanisms contributing to pathogenesis, effective treatment modalities, and prevention strategies that best protect pet health. This article highlights current understanding of the transmission, diagnosis, and management of ehrlichiosis and anaplasmosis in dogs and cats.

Efficacy of a doxycycline treatment regimen initiated during three different phases of experimental ehrlichiosis

Doxycycline is the treatment of choice for canine monocytic ehrlichiosis (CME), a well-characterized disease and valuable model for tick-borne zoonoses. Conflicting reports of clearance of Ehrlichia canis after treatment with doxycycline suggested that the disease phase during which treatment is initiated influences outcomes of these treatments. The purpose of this study was to evaluate the efficacy of a 28-day doxycycline regimen for clearance of experimental E. canis infections from dogs treated during three phases of the disease. Ten dogs were inoculated with blood from E. canis carriers and treated with doxycycline during acute, subclinical, or chronic phases of CME. Daily rectal temperatures and semiweekly blood samples were monitored from each dog, and Rhipicephalus sanguineus ticks were acquisition fed on each dog for xenodiagnosis. Blood collected from dogs treated during acute or subclinical CME became PCR negative for E. canis as clinical parameters improved, but blood samples collected from dogs treated during chronic CME remained intermittently PCR positive. R. sanguineus ticks fed on dogs after doxycycline treatments became PCR positive for E. canis, regardless of when treatment was initiated. However, fewer ticks became PCR positive after feeding on two persistently infected dogs treated with doxycycline followed by rifampin, suggesting that antibiotic therapy can reduce tick acquisition of E. canis.

Experimental infection and co-infection of dogs with Anaplasma platys and Ehrlichia canis: hematologic, serologic and molecular findings

BACKGROUND

Rhipicephalus sanguineus is a ubiquitous tick responsible for transmitting Ehrlichia canis and most likely Anaplasma platys to dogs, as either single or co-infections. The objective of this study was to assess the effects of either simultaneous or sequential experimental infections with E. canis and A. platys on hematological and serological parameters, duration of infection, and efficacy of doxycycline therapy in dogs infected with one or both organisms. Six dogs per group were either uninfected, A. platys infected, E. canis infected, A. platys and E. canis co-infected, A. platys infected and E. canis challenged or E. canis infected and A. platys challenged at day 112 post-infection (PI). Doxycycline treatment was initiated at 211 days PI, followed by dexamethasone immunosuppression beginning 410 days PI.

RESULTS

Initially, transient decreases in hematocrit occurred in all groups infected with E. canis, but the mean hematocrit was significantly lower in the A. platys and E. canis co-infected group. All dogs except the controls developed marked thrombocytopenia after initial infection followed by gradually increased platelet counts by 112 days PI in groups with the single infections, while platelet counts remained significantly lower in the A. platys and E. canis co-infected group. Both sequential and simultaneous infections of A. platys and E. canis produced an enhanced humoral immune response to A. platys when compared to infection with A. platys alone. Likewise, co-infection with E. canis and A. platys resulted in a more persistent A. platys infection compared to dogs infected with A. platys only, but nearly all A. platys infected dogs became A. platys PCR negative prior to doxycycline treatment. E. canis infected dogs, whether single or co-infected, remained thrombocytopenic and E. canis PCR positive in blood for 420 days. When treated with doxycycline, all E. canis infected dogs became E. canis PCR negative and the thrombocytopenia resolved. Despite immunosuppression, neither A. platys nor E. canis DNA was PCR amplified from doxycycline-treated dogs.

CONCLUSIONS

The results of this study demonstrate that simultaneous or sequential infection with A. platys and E. canis can alter various pathophysiological parameters in experimentally infected dogs, and because natural exposure to multiple tick-borne pathogens occurs frequently in dogs, awareness of co-infection is important in clinical practice.

Pathologic evidence of ehrlichiosis in calves inoculated with Ehrlichia chaffeensis

An immunocompetent animal disease model based on infection with Ehrlichia chaffeensis would facilitate research toward understanding mechanisms responsible for the broad range of clinical signs associated with human monocytic ehrlichiosis (HME). The adaptability of this model for the experimental feeding of tick species and stages and for testing therapies comparable to those for human diseases are additional advantages of large animal models. Herein, we summarize pathology reports for calves that developed fatal disease after experimental inoculation with E. chaffeensis. Elevated liver enzyme levels and lung pathology among these calves corroborated earlier reports of severe HME. Thus, an experimental disease model based on infection of outbred immunocompetent hosts with E. chaffeensis could be within our grasp for the first time.

Antibiotic clearance of Ehrlichia canis from dogs infected by intravenous inoculation of carrier blood

Ehrlichia canis is the etiologic agent of canine monocytic ehrlichiosis (CME) and is a useful model for zoonotic tick-borne pathogens, many of which infect dogs. The purpose of this study was to evaluate rifampin and doxycycline regimens for clearance of E. canis infections in addition to alleviation of CME. Beagles were infected with E. canis by intravenous inoculation with carrier blood and treated with either rifampin or doxycycline after the acute phase of CME. Improved hematological values demonstrated that both treatments effectively relieved signs of the disease. Peripheral blood from all dogs became PCR negative after antibiotic treatment, suggesting that these infections were eliminated and that rifampin is an effective alternative chemotherapeutic agent for treatment of CME.