Prevalence of tick-borne pathogens in ticks collected from the wild mountain ungulates mouflon and chamois in 4 regions of France

Ticks are major vectors of various pathogens of health importance, such as bacteria, viruses and parasites. The problems associated with ticks and vector-borne pathogens are increasing in mountain areas, particularly in connection with global climate change. We collected ticks (n = 2,081) from chamois and mouflon in 4 mountainous areas of France. We identified 6 tick species: Ixodes ricinus, Rhipicephalus bursa, Rh. sanguineus s.l., Haemaphysalis sulcata, H. punctata and Dermacentor marginatus. We observed a strong variation in tick species composition among the study sites, linked in particular to the climate of the sites. We then analysed 791 ticks for DNA of vector-borne pathogens: Babesia/Theileria spp., Borrelia burgdorferi s.l., Anaplasma phagocytophilum, A. marginale, A. ovis, and Rickettsia of the spotted fever group (SFG). Theileria ovis was detected only in Corsica in Rh. bursa. Babesia venatorum (2 sites), Borrelia burgdorferi s.l. (B. afzelii and B. garinii; 2 sites) and Anaplasma phagocytophilum (3 sites) were detected in I. ricinus. Anaplasma ovis was detected at one site in I. ricinus and Rh. sanguineus s.l. SFG Rickettsia were detected at all the study sites: R. monacensis and R. helvetica in I. ricinus at the 3 sites where this tick is present; R. massiliae in Rh. sanguineus s.l. (1 site); and R. hoogstraalii and Candidatus R. barbariae in Rh. bursa in Corsica. These results show that there is a risk of tick-borne diseases for humans and domestic and wild animals frequenting these mountain areas.

Lack of efficacy of fenbendazole against Giardia duodenalis in a naturally infected population of dogs in France

Giardiosis is a worldwide intestinal parasitosis, affecting both humans and animals. Treatment in dogs remains limited and the lack of efficacy of the few approved medications is a rising concern. In this study, 23 dogs raised by veterinary students and naturally infected with Giardia duodenalis were treated in home conditions with fenbendazole (50 mg/kg orally for 5 consecutive days). Fecal samples were collected immediately before treatment (FS1), 2-4 days after treatment (FS2) and 8-10 days after treatment (FS3). Giardia duodenalis cyst excretion was measured quantitatively by direct immunofluorescence assay (DFA) at FS1, FS2 and FS3. Molecular typing with a nested PCR targeting the SSU _rDNA locus was also performed at FS1 and FS2. Fecal consistency improved in 16/21 dogs (76%) and mean cyst shedding was reduced by 84% after treatment. However, only 8/23 dogs (35%) achieved therapeutic success (≥90% reduction of cysts) and only 4/23 dogs (17%) had complete elimination of G. duodenalis. Molecular typing showed that dogs harbored only canine-specific assemblages, with a high prevalence of assemblage C in analyzed samples (30/39). We also detected different assemblages after treatment and nucleotide substitutions in assemblage C sequences that have not been described previously. Eight to ten days after treatment, high Giardia cyst excretion was measured, suggesting possible reinfection despite hygiene measures and/or multiplication. These data suggest that fenbendazole treatment may improve fecal consistency but has limited therapeutic efficacy against giardiosis in this population of dogs. Further research is still needed to assess the efficacy of fenbendazole against canine giardiosis.

Detection of tick-borne pathogens in questing Ixodes ricinus in the French Pyrenees and first identification of Rickettsia monacensis in France

Ticks are important vectors of several human and animal pathogens. In this study, we estimated the prevalence of important tick-borne infections in questing ticks from an area in Southwestern France (Hautes-Pyrénées) inhabited by Pyrenean chamois (Rupicapra pyrenaica pyrenaica) experiencing high tick burden. We examined adult and nymph ticks collected by the flag dragging method from 8 to 15 sites in the Pic de Bazès during the years 2009, 2011, 2013 and 2015. PCR assays were conducted on selected ticks for the detection of Borrelia burgdorferi s.l., Babesia spp., Rickettsia spp., spotted fever group (SFG) Rickettsia and Anaplasma phagocytophilum. Randomly selected positive samples were submitted for sequence analysis. A total of 1971 questing ticks were collected including 95 males, 101 females and 1775 nymphs. All collected ticks were identified as Ixodes ricinus. Among them, 696 ticks were selected for pathogen detection and overall prevalence was 8.4% for B. burgdorferi s.l.; 0.4% for Babesia spp.; 6.1% for A. phagocytophilum; 17.6% for Rickettsia spp.; and 8.1% for SFG Rickettsia. Among the sequenced pathogens, we detected in this population of ticks the presence of Babesia sp. EU1 and Rickettsia helvetica, as well as Rickettsia monacensis for the first time in France. The detection of these pathogens in the Pic de Bazès highlights the potential infection risks for visitors to this area and the Pyrenean chamois population.

The Recent Evolution of a Maternally-Inherited Endosymbiont of Ticks Led to the Emergence of the Q Fever Pathogen, Coxiella burnetii

Q fever is a highly infectious disease with a worldwide distribution. Its causative agent, the intracellular bacterium Coxiella burnetii, infects a variety of vertebrate species, including humans. Its evolutionary origin remains almost entirely unknown and uncertainty persists regarding the identity and lifestyle of its ancestors. A few tick species were recently found to harbor maternally-inherited Coxiella-like organisms engaged in symbiotic interactions, but their relationships to the Q fever pathogen remain unclear. Here, we extensively sampled ticks, identifying new and atypical Coxiella strains from 40 of 58 examined species, and used this data to infer the evolutionary processes leading to the emergence of C. burnetii. Phylogenetic analyses of multi-locus typing and whole-genome sequencing data revealed that Coxiella-like organisms represent an ancient and monophyletic group allied to ticks. Remarkably, all known C. burnetii strains originate within this group and are the descendants of a Coxiella-like progenitor hosted by ticks. Using both colony-reared and field-collected gravid females, we further establish the presence of highly efficient maternal transmission of these Coxiella-like organisms in four examined tick species, a pattern coherent with an endosymbiotic lifestyle. Our laboratory culture assays also showed that these Coxiella-like organisms were not amenable to culture in the vertebrate cell environment, suggesting different metabolic requirements compared to C. burnetii. Altogether, this corpus of data demonstrates that C. burnetii recently evolved from an inherited symbiont of ticks which succeeded in infecting vertebrate cells, likely by the acquisition of novel virulence factors.

How virulent infectious diseases emerge from non-pathogenic organisms is a challenging question. Here, we address this evolutionary issue in the case of Q fever. Its causative agent, the intracellular bacterium Coxiella burnetii, is extremely infectious to humans and a variety of animals. However, uncertainty persists regarding its evolutionary origin, including the identity and lifestyle of its ancestors. In this article, we show that C. burnetii arose from a rare evolutionary transformation of a maternally-inherited endosymbiont of ticks into a specialized and virulent pathogen of vertebrates. While arthropod symbionts are typically transmitted maternally and thought not to be infectious to vertebrates, we establish here that one Coxiella symbiont has evolved the necessary adaptations to exploit the vertebrate cell, leading to the emergence of Q fever.

Prevalence of Tritrichomonas foetus infections in French catteries

Recently, Tritrichomonas foetus, the known etiologic agent of bovine trichomonosis was identified in domestic cats in many countries around the world. In felids, this parasite would be a significant cause of large-bowel diarrhoea. Therefore the aim of the present study was to determine for the first time the prevalence of T. foetus infection in French catteries. In this epidemiological survey, rectal swabs from 140 cats participating in three international shows were tested for the presence of motile parasites by microscopy after culturing. The prevalence of T. foetus infection was 14.3% among cats (20/140) and 15.9% among catteries (18/117). These values were similar to those previously obtained in other European countries. Except for the age, no significant associations were found between the presence of T. foetus and various risk factors of infection such as the size of the cattery, the type of food, or the vicinity of a dog. Internal transcribed region of the ribosomal DNA unit was sequenced from the 20 T. foetus isolates identified in this study. They exhibited 100% identity and are homologous with other sequences of strains isolated from domestic cats in other countries.

Diversity, geographic distribution, and habitat-specific variations of microbiota in natural populations of the chicken mite, Dermanyssus gallinae

Dermanyssus gallinae is considered to be the most economically significant ectoparasite to affect egg-laying poultry in Europe. This mite can also act as a vector for a number of pathogens. The array of bacteria associated with D. gallinae mites could provide insight into the biology and population dynamics of arthropods, but at the present time little information is available. To understand the intra- and interpopulation diversity of its associated microbiota, we analyzed the whole internal bacterial community of natural populations of D. gallinae originating from two types of poultry farm habitats (standard and free-range) in two regions of France (Brittany and the Rhone-Alpes). Total DNA was extracted from individual or pooled mites, and polymerase chain reaction temporal temperature gradient gel electrophoresis of 16S rRNA was then done to separate bacterial DNA fragments associated with the host arthropod. A large diversity of bacteria was detected, but principally firmicutes and gamma-Proteobacteria. Between-group analyses of temporal temperature gradient gel electrophoresis-banding patterns revealed that bacterial populations clustered into categories according to their geographic origin and the habitat specifics of the farms. Some degree of stability of bacterial populations was observed within a specific time scale. These results suggest that environmental factors either recent (e.g., poultry farming practices) or long-standing (e.g., geographic isolation) may affect the bacterial communities present in D. gallinae. Further knowledge of the microbiota associated with D. gallinae and its variation would indeed offer new perspectives for biological control methods to prevent the establishment, proliferation, and transmission of pathogenic bacteria.

Modelling population dynamics and response to management options in the poultry red mite Dermanyssus gallinae (Acari: Dermanyssidae)

The poultry red mite Dermanyssus gallinae is a major pest and widespread ectoparasite of laying hens and other domestic and wild birds. Under optimal conditions, D. gallinae can complete its lifecycle in less than 10 days, leading to rapid proliferation of populations in poultry systems. This paper focuses on developing a theoretical model framework to describe the population dynamics of D. gallinae. This model is then used to test the efficacy and residual effect of different control options for managing D. gallinae. As well as allowing comparison between treatment options, the model also allows comparison of treatment efficacies to different D. gallinae life stages. Three different means for controlling D. gallinae populations were subjected to the model using computer simulations: mechanical cleaning (killing once at a given time all accessible population stages), sanitary clearance (starving the mite population for a given duration, e.g. between flocks) and acaricide treatment (killing a proportion of nymphs and adults during the persistence of the treatment). Simulations showed that mechanical cleaning and sanitary clearance alone could not eradicate the model D. gallinae population, although these methods did delay population establishment. In contrast, the complete eradication of the model D. gallinae population was achieved by several successive acaricide treatments in close succession, even when a relatively low treatment level was used.

The poultry red mite (Dermanyssus gallinae): a potential vector of pathogenic agents

The poultry red mite, D. gallinae has been involved in the transmission of many pathogenic agents, responsible for serious diseases both in animals and humans. Nowadays, few effective methods are available to control the ectoparasite in poultry farms. Consequently, this is an emerging problem which must be taken into account to maintain good health in commercial egg production. This paper addresses the vector capacity of the ectoparasite with special emphasis on salmonellae, pathogenic agents responsible for many of the most important outbreaks of food-borne diseases worlwide. It has been experimentally shown that D. gallinae could act as a biological vector of S. enteritidis and natural carriage of these bacteria by the mite on poultry premises has also been reported. It was also found that D. gallinae carried other pathogens such as E. coli, Shigella sp., and Staphylococcus, thus increasing the list of pathogenic agents potentially transmitted by the mite.

Endosymbiotic bacteria living inside the poultry red mite (Dermanyssus gallinae)

This study investigated the endosymbiotic bacteria living inside the poultry red mite collected from five samples of one commercial farm from the UK and 16 farms from France using genus-specific PCR, PCR-TTGE and DNA sequencing. Endosymbiotic bacteria are intracellular obligate organisms that can cause several phenotypic and reproductive anomalies to their host and they are found widespread living inside arthropods. The farm sampled from the UK was positive for bacteria of the genera Cardinium sp. and Spiroplasma sp. From France, 7 farms were positive for Cardinium sp., 1 farm was positive for Spiroplasma sp., 1 farm was positive for Rickettsiella sp. and 2 farms were positive for Schineria sp. However, it was not possible to detect the presence of the genus Wolbachia sp. which has been observed in other ectoparasites. This study is the first report of the presence of endosymbionts living inside the poultry red mite. The results obtained suggest that it may be possible that these bacterial endosymbionts cause biological modifications to the poultry red mite.

Monitoring of Dermanyssus gallinae in free-range poultry farms

Various methods for monitoring Dermanyssus gallinae infestations within free-range egg production units were compared. The study was carried out in five egg-producing free-range poultry buildings infested with D. gallinae. Each farm was divided into six zones (each zone including nest boxes, perches and duckboard) for placing two types of traps (corrugated cardboard and thick card traps) or examining dried droppings for presence of mites. Traps were removed 24 h later, placed into bags and mites were counted at the laboratory using binocular magnification. Droppings were also inspected by eye and mite numbers were estimated. All the methods used allowed us to detect mites although their efficacy differed. The number of mites collected was independent of the type of trap used. Examination of the droppings did not differentiate between buildings with differing mite populations. Placing traps in the nest boxes is a less reliable indicator than placing them on the perches. It appears that the most coherent method for evaluating the D. gallinae population within a free-range flock is to place thick card traps throughout the building, on perches favoured by birds.

Bacterial taxa associated with the hematophagous mite Dermanyssus gallinae detected by 16S rRNA PCR amplification and TTGE fingerprinting

Dermanyssus gallinae (Arthropoda, Mesostigmata) is suspected to be involved in the transmission of a wide variety of pathogens, but nothing is known about its associated non-pathogenic bacterial community. To address this question, we examined the composition of bacterial communities in D. gallinae collected from standard poultry farms in Brittany, France. Genetic fingerprints of bacterial communities were generated by temporal temperature gradient gel electrophoresis (TTGE) separation of individual polymerase chain reaction (PCR)-amplified 16S rRNA gene fragments, followed by DNA sequence analysis. Most of the sequences belonged to the Proteobacteria and Firmicute phyla, with a majority of sequences corresponding to the Enterobacteriales order and the Staphylococcus genus. By using statistical analysis, we showed differences in biodiversity between poultry farms. We also determined the major phylotypes that compose the characteristic microbiota associated with D. gallinae. Saprophytes, opportunistic pathogens and pathogenic agents such as Pasteurella multocida, Erysipelothrix rhusiopathiae and sequences close to the genus Aerococcus were identified. Endosymbionts such as Schineria sp., Spiroplasma sp. Anistosticta, "Candidatus Cardinium hertigii" and Rickettsiella sp. were also present in the subdominant bacterial community. Identification of potential targets within the symbiont community may be considered in the future as a means of ectoparasite control.

Incidence of histomonosis in turkeys in France since the bans of dimetridazole and nifursol

Between April 2003 and March 2005, 113 outbreaks of histomonosis were recorded in standard turkey farms in France, and 15 cases were recorded in turkey breeding centres. Most of the cases were in north-west France, the principal farming area for turkeys. The majority of the cases occurred during the hottest months, from April to September. Large numbers of cases occurred among birds from four to eight weeks of age, but there were some cases in three-week-old birds and some in birds up to 17 weeks of age. In most of the standard turkey flocks the mortality was less than 10 per cent, but it was above 30 per cent in nearly 20 per cent of the outbreaks. In the breeding flocks, the average mortality was 60.2 per cent. The size of the flocks, the sex of the birds and the age at which the first clinical signs appeared did not seem to influence the mortality.

A preliminary study of natural and experimental infection of the lesser mealworm Alphitobius diaperinus (Coleoptera: Tenebrionidae) with Histomonas meleagridis (Protozoa: Sarcomastigophora)

Histomonas meleagridis is a protozoan parasite causing histomoniasis (histomonosis), a disease of gallinaceous fowl. In order to determine whether the lesser mealworm, Alphitobius diaperinus, is capable of harbouring H. meleagridis, the presence of the parasite was tested by polymerase chain reaction in lesser mealworms collected in the field. Parasite DNA was detected in two larvae from two farms undergoing an outbreak of histomoniasis. Insects were also artificially infected, killed after incubation and analysed by polymerase chain reaction for the presence of parasite DNA. After 4 days, two larvae (out of 20) remained positive. In another experimental infection to investigate the viability of histomonads in the larvae, living parasites were detected in five of 20 larvae 4 days after infection. These results indicate that although A. diaperinus can become infected with H. meleagridis it appears to have a low susceptibility to infection and would probably not be a major route of contamination between flocks.

Colonization and organ invasion in chicks experimentally infected with Dermanyssus gallinae contaminated by Salmonella Enteritidis

The poultry red mite (Dermanyssus gallinae) is the most important and common ectoparasite of laying hens in Europe. This haematophagous mite has been experimentally demonstrated to be a vector of Salmonella Enteritidis by acquiring bacteria through the blood meal or cuticular contact. We have evaluated another route of infection by orally inoculating chicks with mites previously infected by S. Enteritidis. Two methods of infecting the mites were tested: mites contaminated by cuticular contact or during the blood meal. After the washing of mites with paraformaldehyde, groups of 10 Salmonella-contaminated mites were inoculated individually into 1-day-old chicks. The titre of the inoculum suspension was evaluated by crushing mites and followed by bacteriological counting. It was 3x10(4) colony-forming units/chick and 2.7x10(6) colony-forming units/chick, respectively, for cuticular contact and orally mediated contamination of mites. Each bird was found to be positive 12 days post-inoculation. Salmonella colonized the intestinal tracts and invaded the livers and spleens. The caecal content concentration reached a mean level of S. Enteritidis of 8.5x10(4) most probable number (MPN) Salmonella/g. This experiment demonstrated the ability of mites to orally infect 1-day-old chicks with subsequent colonization and multiplication of Salmonella. Consequently, mites infected by S. Enteritidis constitute potential reservoir hosts of this bacterium, allowing it to persist in the poultry house as a source of infection for newly introduced animals. If contaminated mites are found in poultry facilities, effective red mite control should be performed before new batches are introduced into the facility.

Detection of Salmonella sp. in Dermanyssus gallinae using an FTA filter-based polymerase chain reaction

Salmonella spp. bacteria are responsible for some of the most important zoonoses worldwide. Because Dermanyssus gallinae (DeGeer) (Acari: Dermanyssidae) has been recently reported to be an experimental vector of Salmonella Enteritidis, it would be of benefit to evaluate the presence of this bacterium in mites. A molecular detection tool associating a simple filter-based DNA preparation with a specific 16S rDNA Salmonella sp. polymerase chain reaction (PCR) amplification was described. The limit of detection with this method was 2 x 10(4) bacteria per mite. To adapt this technique for large-scale studies, two sizes of mite pools were tested and a preliminary investigation was carried out on mites from 16 currently or previously contaminated farms. Mites sampled from one farm of each type were positive for Salmonella, suggesting that Dermanyssus could act as a reservoir between flocks. In further investigations, it will be necessary to carry out a large-scale study to assess the role of D. gallinae in the epidemiology of avian salmonellosis.

Comparison of the VIDAS�system, FTA�filter-based PCR and culture on SM ID for detecting Salmonella in Dermanyssus gallinae

AIMS

To compare different analytical methods for detecting Salmonella in Dermanyssus gallinae.

METHODS AND RESULTS

The detection limit of three Salmonella detection methods [Vitek immunodiagnostic assay (VIDAS) Salmonella immuno-concentration/immunoassay, FTA filter-based PCR, and Salmonella detection and identification medium (SM ID) preceded by a pre-enrichment step] was evaluated by crushing mites in serial dilutions of pure cultures of Salmonella enterica ssp. Enterica serotype Enteritidis. Each method was then compared for its ability to detect Salmonella in artificially contaminated mites. In 105 mites artificially engorged with Salm. Enteritidis-contaminated blood, Salmonella was isolated from 68 samples of the samples cultured on SM ID and tests were positive for Salmonella using FTA filter-based PCR and VIDAS in 77 and 65 samples, respectively. Using SM ID as our reference method, specificities and sensitivities were 97% and 94% and 73% and 98.5% for VIDAS and PCR, respectively.

CONCLUSIONS

Each method allowed the detection of Salmonella in contaminated mites and is usable for screening mites. PCR is more sensitive but less specific than VIDAS for detecting Salmonella.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first time that the VIDAS has been used to detect pathogens in vectors. The development of analytical methods for Salmonella detection in mites is a necessary step in the study of the role of D. gallinae as a vector of salmonellae and to check the contamination of D. gallinae in poultry facilities.

Experimental infection of Salmonella Enteritidis by the poultry red mite, Dermanyssus gallinae

Dermanyssus gallinae is an important ectoparasite of laying hens in Europe and it is suspected of being a vector of pathogens. We carried out an in vitro study to evaluate the role of D. gallinae as a vector of Salmonella enterica subsp. enterica serotype Enteritidis. Two means of infecting the mite were tested: through the blood meal and after cuticular contact. Mites became carriers of Salmonella immediately after the infection with 29% and 53%, respectively, for oral route and cuticular contact. This percentage increased over time until it reached 95% (D7) and 80% (D14). The numerical identification of bacteria on the selective medium SM ID demonstrated the multiplication of Salmonella inside previously infected mites. In addition, transovarial passage as well as transstadial passage (from N1 to N2 stages) were demonstrated. Moreover, the observation of a negative effect of Salmonella on Dermanyssus oviposition was also observed. Finally, previously infected mites were able to contaminate the blood during the blood meal. Therefore, it appears that D. gallinae may act as a biological vector of S. Enteritidis under experimental conditions. It may represent a suitable environment for the development of Salmonella and could be an additional factor for the persistence of salmonellosis infection between successive flocks.

Comparison of four methods of extracting DNA from D. gallinae (Acari: Dermanyssidae)

Dermanyssus gallinae is one of the most serious ectoparasites of poultry and it has been implicated as a vector of several major pathogenic diseases. Molecular detection of such pathogens in mites is crucial and therefore, an important step is the extraction of their DNA from mites. So, we compared four DNA extraction protocols from engorged and unfed individual mites: a conventional method using a Cethyl Trimethyl Ammonium Bromide buffer (CTAB), a Chelex resin, a Qiamp DNA extraction kit and a more recent one filter-based technology (FTA). The DNA samples have been tested for their ability to be amplified by an amplification of a D. gallinae 16S rRNA gene region. The best results were obtained using CTAB and Qiagen methods at the same time with unfed and engorged mites (96% and 100% of amplified samples). FTA produced similar results when using unfed mites but not when processing engorged ones (96% and 70%). Finally, the Chelex method was the least efficient in terms of DNA amplification, especially when applied on engorged individuals (50%). The possible inhibitor role of these Chelex extracted DNA was demonstrated by the means of a PCR control on PUC plasmid. No difference was observed with CTAB, Qiamp DNA extraction kit or FTA methods using DNA extracted one year before.

Histomonas meleagridis in Turkeys: Dissemination Kinetics in Host Tissues After Cloacal Infection

Histomonas meleagridis is a flagellated protozoa causing histomoniasis, a disease of gallinaceous fowl. This disease is characterized by necrotic typhlitis, hepatitis, and high mortality, especially in turkeys. In an attempt to detect the progression of H. meleagridis in the turkey, birds were infected via the cloaca. Between d 0 and 19, a group of 4 turkeys was killed and autopsied every 3 d. Cecal and hepatic lesion scores were used to measure severity of infection. For each turkey, 15 tissue samples were taken. Another group of 3 infected turkeys were placed separately, and samples of cecal and intestinal stool were collected every 3 d. Samples were analyzed by PCR. For samples of cecal droppings, cecum, cecal content, rectum, proventriculus, and bursa of Fabricius, the number of birds detected as positive by PCR followed the evolution of the lesion scores. Within the liver, the parasite DNA was detected only in some severe lesions. The parasite DNA was also detected in duodenum, jejuno-ileum, spleen, heart, lungs, and brain samples. The parasite DNA was not detected in the blood, kidneys, pancreas, or muscle of the thigh. Results of the PCR were in agreement with the evolution of the clinical signs and of the cecal and liver lesions.

Infectivity ofHistomonas meleagridisin ducks

The susceptibility of mule and muscovy ducks to "blackhead" disease caused by Histomonas meleagridis was studied, using an experimental intracloacal inoculation. Turkeys were used as controls. Morbidity, mortality and body weight gain were recorded regularly during the experiments. A direct examination of the caecal content was made to determine the absence or presence of the parasite. Gross and microscopic lesions were observed on days 7, 14, 21, 28 and 35 post infection to evaluate any clinical histomoniosis in ducks and to appraise the histomonad's carriage. A scoring system was developed both for gross and histological lesions of the caecum and liver. Infected mule and muscovy ducks (n = 83) never developed any clinical signs of histomoniasis. Weight gains of infected mule and muscovy ducks were similar to those of uninfected ducks. In 67% of the ducks (56/83), it was possible to demonstrate the parasite in the caecal content throughout the experiment. Typical macroscopic caecal lesions were observed in five of the ducks between days 7 and 21 post infection, with a caecal necropsy main lesion score (MLS = 1.6) less severe than that in turkeys (MLS = 2.9). Only caecal histological lesions occurred in six of the cases. Therefore, ducks do not seem to be a susceptible host for "blackhead" but may act as carrier animals for H. meleagridis. The virulence was apparently not changed, since 67% of turkeys (10/15) infected with the caecal content of positive ducks displayed classical signs of blackhead disease. Even if H. meleagridis alone does not represent a substantial danger in the duck production, its infectivity should to be taken into account in the transmission to more susceptible species.

Vectorial role of some dermanyssoid mites (Acari, Mesostigmata, Dermanyssoidea)

Among transmissible diseases, vectorial diseases represent a major problem for public health. In the group of acarina, while ticks are the most commonly implicated vectors, other arthropods and notably Dermanyssoidea are also involved in the transmission of pathogenic agents. Since the role of this superfamily is at present largely unknown, we have reviewed the vectorial role of these mites in the appearance, survival and propagation of pathogens. Various authors have shown that Dermanyssoidea are implicated in the transmission of both bacteria (Salmonella, Spirocheta, Rickettsia or Pasteurella) and viruses (equine encephalitis viruses, West Nile virus, Fowl pox virus, the virus causing Newcastle disease and tick borne encephalitis viruses or hantaviruses). Finally, some authors have also shown their role in the transmission of some protozoa and filaria. As the vectorial character of such mites has been more clearly demonstrated (Dermanyssus gallinae, Omithonyssus bacoti and Allodermanyssus sanguineus), it would be interesting to continue studies to better understand the role of this superfamily in the epidemiology of certain zoonoses.

Detection of Histomonas meleagridis in turkeys cecal droppings by PCR amplification of the small subunit ribosomal DNA sequence

Histomonas meleagridis is a protozoan parasite that may cause histomoniasis, a disease of gallinaceous fowl characterized by necrotic typhlitis, hepatitis and high mortality. Diagnosis of this disease is based on direct identification or on cultivation of the parasite. With the aim of developing more sensitive, rapid and useful tools for parasite detection, PCR that amplified a DNA target of 209 pb of the 18S rRNA gene was designed to detect the genome of H. meleagridis and to differentiate it from the genome of Tetratrichomonas gallinarum, another common protozoan parasite of fowl. The sensitivity of the test was evaluated using serial diluted samples of cultured H. meleagridis and showed positive amplification for concentrations comprised between 10 and 10(-1)parasites/ml of culture. The sensitivity for cecal droppings samples was assessed using spiked material and was comprised between 3 x 10(3) and 3 x 10(5)parasites/ml of stool. The reliability of the PCR for the detection of Histomonas infection was also evaluated by experimental infection of turkeys. Results of the PCR appeared to be in agreement with the development of the clinical signs and of the cecal lesions. The PCR developed in this study may be a useful tool in the detection and identification of H. meleagridis for rapid, routine screening as a supplement to direct identification or cultivation of the parasite.

Molecular phylogenies of Blastocystis isolates from different hosts: implications for genetic diversity, identification of species, and zoonosis

Small-subunit (SSU) rRNA gene sequences were obtained by PCR from 12 Blastocystis isolates from humans, rats, and reptiles for which elongation factor 1alpha (EF-1alpha) gene sequences are already available. These new sequences were analyzed by the Bayesian method in a broad phylogeny including, for the first time, all Blastocystis sequences available in the databases. Phylogenetic trees identified seven well-resolved groups plus several discrete lineages that could represent newly defined clades. Comparative analysis of SSU rRNA- and EF-1alpha-based trees obtained by maximum-likelihood methods from a restricted sampling (13 isolates) revealed overall agreement between the two phylogenies. In spite of their morphological similarity, sequence divergence among Blastocystis isolates reflected considerable genetic diversity that could be correlated with the existence of potentially >/=12 different species within the genus. Based on this analysis and previous PCR-based genotype classification data, six of these major groups might consist of Blastocystis isolates from both humans and other animal hosts, confirming the low host specificity of Blastocystis. Our results also strongly suggest the existence of numerous zoonotic isolates with frequent animal-to-human and human-to-animal transmissions and of a large potential reservoir in animals for infections in humans.

Molecular phylogenies of Blastocystis isolates from different hosts: implications for genetic diversity, identification of species, and zoonosis

Small-subunit (SSU) rRNA gene sequences were obtained by PCR from 12 Blastocystis isolates from humans, rats, and reptiles for which elongation factor 1alpha (EF-1alpha) gene sequences are already available. These new sequences were analyzed by the Bayesian method in a broad phylogeny including, for the first time, all Blastocystis sequences available in the databases. Phylogenetic trees identified seven well-resolved groups plus several discrete lineages that could represent newly defined clades. Comparative analysis of SSU rRNA- and EF-1alpha-based trees obtained by maximum-likelihood methods from a restricted sampling (13 isolates) revealed overall agreement between the two phylogenies. In spite of their morphological similarity, sequence divergence among Blastocystis isolates reflected considerable genetic diversity that could be correlated with the existence of potentially >/=12 different species within the genus. Based on this analysis and previous PCR-based genotype classification data, six of these major groups might consist of Blastocystis isolates from both humans and other animal hosts, confirming the low host specificity of Blastocystis. Our results also strongly suggest the existence of numerous zoonotic isolates with frequent animal-to-human and human-to-animal transmissions and of a large potential reservoir in animals for infections in humans.

A Mathematical Model of the Population Dynamics of Heterakis Gallinarum in Turkeys (Meleagridis Gallopavo)

Heterakis gallinarum is a relatively nonpathogenic organism, but it is important as the transport host for the pathogenic protozoan Histomonas meleagridis. A mathematical model was developed to describe the population dynamics of Heterakis gallinarum in a turkey flock to study its kinetics in a number of hosts. The model includes quantitative (parasite burden) and qualitative (number of hosts without mature parasite) descriptions of these dynamics. To understand the role of Heterakis as a transport host, the various elements that delay the beginning of development of the parasite population (e.g., necessary delay of larval stage, the probability of having a male and female in the same host) were taken into account. From published data, the negative binomial distribution parameter k = 0.24, which described the aggregated distribution of the Heterakis among the hosts, was calculated. The sensibility study showed that when the k parameter decreased (i.e., when the population was more aggregated), infestation increased quantitatively (mean parasite burden increased) but not qualitatively (the number of host without mature parasite increased). The model demonstrated that the population dynamics of Heterakis takes time; for instance, with an aggregated population of Heterakis at d 90, the host is mainly free of adult parasite. These results may be used in the future to test the role of Heterakis in the spread of Histomonas.

In vitro effect of essential oils from Cinnamomum aromaticum, Citrus limon and Allium sativum on two intestinal flagellates of poultry, Tetratrichomonas gallinarum and Histomonas meleagridis

Essential oils may be effective preventive or curative treatments against several flagelated poultry parasites and may become primordial either to organic farms, or as more drugs are bannished. The anti-flagellate activity of essential oils obtained from fresh leaves of Cinnamomum aromaticum, Citrus limon pericarps and Allium sativum bulbs was investigated in vitro on Tetratrichomonas gallinarum and Histomonas meleagridis. On T. gallinarum, the minimal lethal concentration (MLC) at 24 hours was 0.25 microliter/ml for C. aromaticum oil, and 0.125 microliter/ml for C. limon and A. sativum oils. On H. meleagridis, MLC was 0.5 microliter/ml for C. aromaticum oil and 1 microliter/ml for C. limon and A. sativum oils at 24 and 48 hours. Moreover, no synergistic effects were evidenced in vitro. The essential oil constituents, based on their GC retention times have been also identified. The major component is trans-cinnamaldehyde (79%) for C. aromaticum; limonene for C. limon (71%) and diallyl tri- and disulfide (79%) for A. sativum. Even if concentration and protocol adaptations are required for successful in vivo treatments, it appears that these oils may be useful as chemotherapeutic agents against several poultry parasites.

In vitro activity of therapeutic drugs against Histomonas meleagridis (Smith, 1895)

Histomoniasis or blackhead is a life-threatening disease of turkeys that is caused by a flagellated protozoan, Histomonas meleagridis. The development of an assay to measure the sensitivity of drugs traditionally used against this parasite, as reputed to be effective against other protozoan parasites, is described. The in vitro minimum lethal concentrations (MLC), time for drug efficacy, and parasite viability after removal of residual drugs were determined. Three of the 10 tested drugs, fenbendazole, albendazole, and sulfadiazine, were found to be ineffective against H. meleagridis. Nifursol, the only compound still authorized as a feed additive in Europe, is an inhibiting agent but is not lethal in vitro. Roxarsone, an arsenical derivate similar to nitarsone (the only authorized drug in United States), is effective at high concentration (200 microg/mL) after a long exposure (48 h). The lethal activity of dimetridazole, metronidazole, ronidazole, tinidazole, and furazolidone in vitro was demonstrated. Dimetridazole (MLC = 25 microg/mL after 6 h of exposure), metronidazole (MLC = 50 microg/mL after 24 h), and furazolidone (MLC = 50 microg/mL after 24 h) are rapidly effective at low concentrations. These results confirm the effectiveness of dimetridazole, a drug that has been used in the treatment and prevention of blackhead. In May 2002 this compound was removed as feed additive in Europe.

First in vitro cycle of the chicken mite, Dermanyssus gallinae (DeGeer 1778), utilizing an artificial feeding device

The red poultry mite, Dermanyssus gallinae, is one of the most economically deleterious ecto-parasites of layer hens worldwide. D. gallinae is difficult to eliminate from infested poultry farms, and even to study, because it resides on the host only during the bloodmeal at night, and hides in the crevices of poultry houses during the day. Here, the life-cycle of D. gallinae was reproduced entirely in vitro. Mites were incubated in a glass pipette at 30 degrees C, 60-95 degrees relative humidity and total darkness. A feeding apparatus, composed of a membrane, reservoir and blood was fitted on the pipette during bloodmeals. We tested feeding rates on blood mixed with 1 of 3 anti-coagulants (EDTA, heparin and trisodium citrate) at different concentrations, and biological and artificial membranes. The best engorgement and survival rates for all 3 haematophagous life-stages of the parasite were observed in 1-day-old chick membranes and heparinized (0.02 mmo/ml) blood. We then describe the steps in developing a complete self-sustaining in vitro life-cycle. A colony of mites was maintained in vitro for 7 generations. Losses in the first generation were heavy, but survival had multiplied 5-fold by the fifth generation. We hypothesize that heavy mortality rates during the first life-cycle correspond to selective pressure: only the mites which fed and survived in vitro were able to reproduce.

Phylogenetic position of the trichomonad parasite of turkeys, Histomonas meleagridis (Smith) Tyzzer, inferred from small subunit rRNA sequence

The phylogenetic position of the trichomonad, Histomonas meleagridis was determined by analysis of small subunit rRNAs. Molecular trees including all identified parabasalid sequences available in data bases were inferred by distance, parsimony, and likelihood methods. All reveal a close relationship between H. meleagridis, and Dientamoeba fragilis. Moreover, small subunit rRNAs of both amoeboid species have a reduced G + C content and increased chain length relative to other parabasalids. Finally, the rRNA genes from H. meleagridis and D. fragilis share a recent common ancestor with Tritrichomonasfoetus, which exhibits a more developed cytoskeleton. This indicates that Histomonas and Dientamoeba secondarily lost most of the typical trichomonad cytoskeletal structures and hence, do not represent primitive morphologies. A global phylogeny of parabasalids revealed significant discrepancies with morphology-based classifications, such as the polyphyly of most of the parabasalid families and classes included in our study.

Ten-year long monitoring of laboratory mouse and rat colonies in French facilities: a retrospective study

From 1988 to 1997, a total of 69 mouse colonies and 36 rat colonies were examined for the presence of antibodies to 14 indigenous viruses of mice and rats. Among mouse viruses, high positivity rates were observed with mouse hepatitis virus (MHV), Theiler's encephalomyelitis virus (THEMV), minute virus of mice (MVM), Sendai virus and pneumonia virus of mice (PVM); the prevalence rates were high in rats with Khilam's rat virus (KRV), THEMV, Toolan's H-1 virus, Sendai virus, Parker's rat coronavirus (RCV/SDA) and PVM. During the last decade, the prevalence of some agents such as MHV, Sendai virus, THEMV, PVM and MVM has apparently decreased although they were still present in 1997 (except for PVM). Another point is the constant increase of colonies found free of viruses through this decade, demonstrating the efforts of the French research community to increase the quality of hygiene in laboratory animals.

Infection with Toxoplasma gondii RH and Prugniaud strains in mice, rats and nude rats: kinetics of infection in blood and tissues related to pathology in acute and chronic infection

Since mice and rats are the most studied models of experimental toxoplasmosis, the aim of this work was to analyze the outcome of Toxoplasma infection in mice, rats and congenitally athymic nude rats; for this purpose, the parasitic load in different organs and the anatomic-pathological characteristics of infection were investigated in these animals. The data obtained after infection with two different strains and stages of Toxoplasma gondii (RH tachyzoites and Prugniaud cysts) concerned the following organs: brain, mesenteric lymph nodes, blood, spleen, heart, lungs, diaphragm and liver. In Fischer rats, the infection with either the Prugniaud or the RH strains displayed similar characteristics: after a peak in the parasite load, a complete disappearance of parasites was observed, except in the brain of Prugniaud strain-infected rats where toxoplasmas were evidenced throughout the experiment. In OF1 mice, where infection by the RH tachyzoites was lethal, infection with the Prugniaud strain led to survival; the parasitic burden peaked in the different organs and was then undetectable, except in the brain where toxoplasmas were still present during the chronic phase. Like mice, nude rats did not survive to the RH infection. Interestingly, for all the animals the observed histopathological changes in the infected organs, although more or less obvious in the acute phase, were not very severe in almost all cases. For instance, mice, although more susceptible to infection than rats, did not present more severe lesions. They consisted in a discrete inflammation with some focal areas of necrosis in some organs such as brain, liver and heart. Our results support the assumption that rats and nude rats constitute interesting experimental models relevant to either human acute toxoplasmosis, chronic toxoplasmosis, or disseminated toxoplasmosis in AIDS patients.

Protective immunity in the rat model of congenital toxoplasmosis and the potential of excreted-secreted antigens as vaccine components

Toxoplasma infection is a major cause of severe foetal pathology both in humans and in domestic animals, particularly sheep. We have previously reported the development of an experimental model to study congenital toxoplasmosis in the rat. Here we demonstrate that, as in humans, total protection against congenital toxoplasmosis can be achieved regardless of the strain of Toxoplasma gondii used to infect rats, or when initial and challenge infections were carried out with different strains. Chronic infection is associated with a highly specific immunity that involves both B-and T-cell responses beginning at day 10 postinfection. The antibody isotype analysis revealed that whereas immunoglobulin (Ig)G2b is the major elicited isotype, no IgG1 antibodies are detected. T cell proliferation was assayed using crude Toxoplasma extracts or excretory-secretory antigens (ESA). The analysis of T cell supernatants showed the specific secretion of both interleukin-2 and interferon-gamma by activated T cells. Immunization of rats before pregnancy with either crude Toxoplasma extracts or with ESA elicited a B cell response that included antibodies of the IgG1 isotype and conferred on the newborns high levels of protection. Preliminary experiments of immunization using two HPLC-purified ESA, GRA2 and GRA5, conferred, a significant protection although to a lesser extent. This experimental model represents an attractive model for the identification of future vaccine candidates against congenital toxoplasmosis.

Pathology, diagnosis and epidemiology of the rodent Helicobacter infection

Since the first isolation of Helicobacter pylori from humans in 1983, 18 Helicobacter species have been identified during the last decade in domestic and laboratory animals. Several Helicobacter species have been isolated from the gastrointestinal tracts of various mammalian species and birds. Helicobacter hepaticus, H. muridarum, H. bilis, H. rodentium and Flexispira rappini have been isolated from mice. Among these species, only H. hepaticos has been clearly recognized as a pathogen. Indeed, it displays the pathogenic potential to elicit hepatitis in several strains of mice; moreover in A/JCr mice, it is strongly associated with hepatic cancer. Among the five murine helicobacter species, apart from H. hepaticus, F. rappini has not been found associated with lesions, H. muridarum has been observed in gastric glands of mice with chronic gastritis, and H. bilis has been reported in the liver of mice with chronic hepatitis. When associated with H. rodentium, H. bilis is able to induce diarrhea in SCID mice. In no case has pathogenicity of a single species been clearly proven. In rats, H. trogontum and H. muridarum have been isolated from the intestine, without any information concerning their respective pathogenicity. H. cinaedi and H. cholecystus have been identified from the intestine and the gallbladders of hamsters, respectively. The diagnosis of Helicobacter species by polymerase chain reaction (PCR) is a rapid, specific and sensitive technique. One of the most promising diagnostic techniques of these infections seems to be the PCR detection of Helicobacter sp. from feces based on the 16S rRNA sequences, then a restriction enzyme analysis to identify the actual species. Several drug regimens have also been evaluated to eradicate H. hepaticus from mice. Helicobacter infections, particularly H. hepaticus and H. bilis, seem to be widespread in laboratory mouse colonies and have also been detected from commercial breeders.

Toxoplasma gondii: kinetics of the dissemination in the host tissues during the acute phase of infection of mice and rats

Mice and rats differ in their susceptibility to Toxoplasma gondii infection. Here we have compared the parasitological parameters of acute infection in both mice and rats infected either orally with cysts of Prugniaud strain or intraperitoneally (ip) with tachyzoites of the RH strain. The animals were killed at regular interval during the acute phase, and the parasitic burden in mesenteric lymph nodes, spleen, liver, diaphragm, heart, lungs, brain, and blood was assessed by a tissue culture method in MRC5 fibroblast cells. Mice infected with the RH strain showed a drastic increase of the parasitic load in all organs (up to 10 (8) parasites / g of organs), and then died. When mice were infected with 50 cysts of Prugniaud strain, parasites were first observed in mesenteric lymph nodes, spleen, and lungs and then in other organs. In rats, infection with 1200 cysts of the same strain led to a similar pattern; however, the chronology of the infected organs changed when they were infected with RH strain tachyzoites. These results suggest that the parasites, present first in the peritoneal cavity in the case of RH ip infection, infect all the adjacent organs and then the blood which disseminates the tachyzoites all over the organism. In contrast, after an oral infection, the parasite crosses the intestinal barrier to reach the mesenteric lymph nodes and then the spleen and are finally distributed by the blood throughout the organism. We also showed that following infection with a lethal or a sublethal doses of the Prugniaud strain, the parasitic burden in the studied organs was similar and therefore does not directly correlate with the death of the mice.

Effective eradication of pinworms (Syphaciamuris, Syphacia obvelata and Aspiculuris tetraptera) from a rodent breeding colony by oral anthelmintic therapy

An oral combination of piperazine and ivermectin was used over a 6-week period for treating three different colonies of mice or rats infested with Syphacia obvelata, Syphacia muris or Aspiculuris tetraptera. No acute toxic effect was found in transgenic lines of mice or rats with these products in a preliminary trial. The colonies were treated with piperazine, 2.1 mg/ml in tap water for 2 weeks, then with ivermectin, 0.007 mg/ml, in tap water for the third and fourth weeks, and finally with piperazine for two further weeks. Hygiene measures such as a complete cage change, thorough disinfection and cleaning of the rooms were associated with the treatment. All examinations subsequent to completion of treatment have proved negative for further parasites.

Antigenicity and immunogenicity of P30-derived peptides in experimental models of toxoplasmosis

P30, also referred to as SAG-1, is now recognized as a major Toxoplasma gondii antigen potentially important for both diagnosis and immunoprophylaxis of toxoplasmosis. By using predictive algorithms, five synthetic peptides (48-67, 82-102, 213-230, 238-256 and 279-285) derived from P30, were investigated for B- and T-cell determinants in mouse and rat experimental models. Antibody recognition appeared more broadly distributed along the P30 sequence, whereas T-cell recognition was mainly targeted on the 238-256 peptide. In the absence of any carrier protein, this peptide induced a B- and T-cell immune response independent of the route of immunization (oral route or subcutaneous injection). This peptide (238-256) induced multiple antibody isotypes. In contrast with the 238-256 peptide, the 48-67 peptide, either free or in the form of a multiple antigenic peptide (MAP) construct or the 279-295 peptide, elicited antibodies associated with a TH2 response. This study reports for the first time the analysis of the antigenic and immunogenic properties of P30-derived peptides and are potentially useful for vaccinal strategies incorporating the P30 Toxoplasma gondii antigen.

Pathology of Toxoplasma gondii infection in the nude rat. An experimental model of toxoplasmosis in the immunocompromised host?

Genetically athymic nu/nu (nude) rats, deficient in T cells, die from infection with various Toxoplasma gondii strains, including RH and Prugniaud strains. In contrast, these strains cause chronic infections without apparent symptoms in immunocompetent non-nude rats. We show here that nude rats die in two to three weeks after RH infection and three to four weeks after Prugniaud infection. Histological examination of brains from nude rats at different time points after infection, revealed an absence of lesions after RH strain infection and cysts with usually no inflammation after Prugniaud infection. Lungs from nude rats developed a fibrin alveolitis using either strain, whereas myocarditis with focal areas of necrosis were observed only after Prugniaud infection. Cysts and, in some cases, tachyzoites in the necrotic lesions were easily identifiable. The two strains of T. gondii elicited in nude rats a granulomatous hepatitis that only differed in intensity. Spleen and mesenteric lymph nodes appeared totally non reactive in both cases. This model allows immunological and parasitological studies by comparison with immunocompetent rat infection. Published data concerning toxoplasma pathology in AIDS, therefore, suggest that acute toxoplasma infection in nude rats may be a useful model for studying disseminated forms of toxoplasma infection found in AIDS patients.

Rat model of congenital toxoplasmosis: rate of transmission of three Toxoplasma gondii strains to fetuses and protective effect of a chronic infection

The incidence of congenital toxoplasmosis in Fischer rats infected between the 8th and 12th days of pregnancy with three different strains of Toxoplasma gondii (RH, 76K, and Prugniaud) were 58.2, 35.2, and 62.8%, respectively. No infected fetuses were collected from rats previously infected with RH or Prugniaud strain parasites, even if the rats were reinfected during pregnancy. Since pups from chronically infected mothers are protected from congenital toxoplasmosis, rat infection could thus constitute a relevant model for immunological studies and vaccine design.