Epidemiology and pathogenicity of M. equirhinis in equine respiratory disorders.

Mycoplasmas are pathogens involved in respiratory disorders of various animal hosts. In horses, Mycoplasma (M.) equirhinis is the species most frequently detected in clinical respiratory specimens, with a prevalence of 12-16%, but its clinical implication in equine respiratory disorders remains unclear. Here we screened 1948 clinical specimens for the presence of M. equirhinis. The samples were both tracheal washes (TW) and bronchoalveolar lavages (BAL) collected by veterinarians in France in day-to-day work between 2020 and 2022. The samples were associated with a standardized form that served to collect key general and clinical information, such as horse age, breed, and living environment. M. equirhinis was detected using a combination of culture and post-enrichment PCR. Other diagnostic data included virology and bacteriology as well as neutrophil counts, when available. Prevalence of M. equirhinis was examined as a function of a clinical score based on four significant clinical signs (nasal discharge, cough, dyspnoea, and hyperthermia). Multivariate logistic regression analysis was run to identify risk factors for the presence of M. equirhinis, and comparative prevalence analysis was used to test for association with other bacteria and viruses. TW and BAL were analysed independently, as we found that TW samples were associated with a higher prevalence of M. equirhinis. As prevalence remained steady whatever the clinical score, M. equirhinis cannot be considered a primary pathogen. M. equirhinis was more frequently isolated in thoroughbreds and trotters and in horses living exclusively stabled compared to other horses or other living environments. M. equirhinis was never detected in BAL specimens with a 'normal' neutrophil count, i.e. 5%, suggesting it could be associated with an inflammatory response, similar to that observed in equine asthma. Prevalence of M. equirhinis was shown to increase in the presence of other bacteria such as Streptococcus equi subsp. zooepidemicus (S. zoo) or viruses, and S. zoo load was higher in M. equirhinis-positive samples, suggesting a potential increase of clinical signs in the event of co-infection.

One Health surveillance of West Nile and Usutu viruses: a repeated cross-sectional study exploring seroprevalence and endemicity in Southern France, 2016 to 2020.

BackgroundWest Nile virus (WNV) and Usutu virus (USUV), two closely related flaviviruses, mainly follow an enzootic cycle involving mosquitoes and birds, but also infect humans and other mammals. Since 2010, their epidemiological situation may have shifted from irregular epidemics to endemicity in several European regions; this requires confirmation, as it could have implications for risk assessment and surveillance strategies.AimTo explore the seroprevalence in animals and humans and potential endemicity of WNV and USUV in Southern France, given a long history of WNV outbreaks and the only severe human USUV case in France in this region.MethodsWe evaluated the prevalence of WNV and USUV in a repeated cross-sectional study by serological and molecular analyses of human, dog, horse, bird and mosquito samples in the Camargue area, including the city of Montpellier, between 2016 and 2020.ResultsWe observed the active transmission of both viruses and higher USUV prevalence in humans, dogs, birds and mosquitoes, while WNV prevalence was higher in horses. In 500 human samples, 15 were positive for USUV and 6 for WNV. Genetic data showed that the same lineages, WNV lineage 1a and USUV lineage Africa 3, were found in mosquitoes in 2015, 2018 and 2020.ConclusionThese findings support existing literature suggesting endemisation in the study region and contribute to a better understanding of USUV and WNV circulation in Southern France. Our study underlines the importance of a One Health approach for the surveillance of these viruses.

Molecular assessment of Theileria equi and Babesia caballi prevalence in horses and ticks on horses in southeastern France.

Equine piroplasmosis (EP) is a tick-borne disease caused by Babesia caballi and Theileria equi that is potentially emerging in non-endemic countries. We conducted a descriptive study to investigate EP prevalence and spatial distribution in an endemic region: the Camargue and the Plain of La Crau in France. In spring 2015 and 2016, we carried out sampling at stables (total n = 46) with a history of horses presenting chronic fever or weight loss. Overall, we collected blood from 632 horses, which were also inspected for ticks; these horses had been housed in the target stables for at least 1 year. We obtained 585 ticks from these horses and described land use around the stables. Real-time PCR was employed to assess T. equi and B. caballi prevalence in the horses and in the ticks found on the horses. For the horses, T. equi and B. caballi prevalence was 68.6% and 6.3%, respectively. For the ticks found on the horses, prevalence was 28.8% for T. equi and 0.85% for B. caballi. The most common tick species were, in order of frequency, Rhipicephalus bursa, R. sanguineus sl., Hyalomma marginatum, Haemaphysalis punctata, and Dermacentor sp. Horses bearing Rhipicephalus ticks occurred in wetter zones, closer to agricultural areas, permanent crops, and ditches, as well as in drier zones, in the more northern countryside. Compared to horses bearing R. bursa, horses bearing R. sanguineus sl. more frequently occurred near the Rhone River. Prevalence of T. equi in the ticks was as follows: Hyalomma marginatum (43%), Dermacentor sp. (40%), R. bursa (33%), R. sanguineus sl. (19%), and Haemaphysalis punctata (17%). In contrast, B. caballi only occurred in Dermacentor sp. (20%) and R. bursa (1%).

Seroprevalence of horses to Coxiella burnetii in an Q fever endemic area.

Coxiella burnetii can infect many animal species, but its circulation dynamics in and through horses is still unclear. This study evaluated horse exposure in an area known to be endemic for ruminants and humans. We assessed antibody prevalence in horse serum by ELISA, and screened by qPCR horse blood, ticks found on horses and dust from stables. Horse seroprevalence was 4% (n = 335, 37 stables) in 2015 and 12% (n = 294, 39 stables) in 2016. Of 199 horses sampled both years, 13 seroconverted, eight remained seropositive, and one seroreverted. Seropositive horses were located close to reported human cases, yet none displayed Q fever-compatible syndromes. Coxiella DNA was detected in almost 40% of collected ticks (n = 59/148 in 2015; n = 103/305 in 2016), occasionally in dust (n = 3/46 in 2015; n = 1/14 in 2016) but never in horse blood. Further studies should be implemented to evaluate if horses may be relevant indicators of zoonotic risk in urban and suburban endemic areas.

One particular Anaplasma phagocytophilum ecotype infects cattle in the Camargue, France.

BACKGROUND: Anaplasma phagocytophilum is a zoonotic tick-borne pathogen responsible for granulocytic anaplasmosis, a mild to a severe febrile disease that affects man and several animal species, including cows and horses. In Europe, I. ricinus is the only proven vector for this pathogen, but studies suggest that other tick genera and species could be involved in its transmission. Our objective was to assess the presence and genetic diversity of A. phagocytophilum in domestic animals and different tick species from the Camargue region, located in the south of France. METHODS: A total of 140 ticks and blood samples from 998 cattle and 337 horses were collected in Camargue and tested for the presence of A. phagocytophilum DNA by msp2 quantitative real-time PCR. Molecular typing with four markers was performed on positive samples. RESULTS: Anaplasma phagocytophilum DNA was detected in 6/993 (0.6%) cows, 1/20 (5%) Haemaphysalis punctata, 1/57 (1.75%) Rhipicephalus pusillus, and was absent in horses (0%). All cattle A. phagocytophilum presented a profile identical to an A. phagocytophilum variant previously detected in Dermacentor marginatus, Hyalomma marginatum, and Rhipicephalus spp. in Camargue. CONCLUSIONS: Our results demonstrate that one particular A. phagocytophilum variant infects cattle in Camargue, where I. ricinus is supposed to be rare or even absent. Dermacentor marginatus, Rhipicephalus spp. and Hyalomma spp., and possibly other tick species could be involved in the transmission of this variant in this region.

An Integrative Eco-Epidemiological Analysis of West Nile Virus Transmission.

West Nile disease, caused by the West Nile virus (WNV), is a mosquito-borne zoonotic disease affecting humans and horses that involves wild birds as amplifying hosts. The mechanisms of WNV transmission remain unclear in Europe where the occurrence of outbreaks has dramatically increased in recent years. We used a dataset on the competence, distribution, abundance, diversity and dispersal of wild bird hosts and mosquito vectors to test alternative hypotheses concerning the transmission of WNV in Southern France. We modelled the successive processes of introduction, amplification, dispersal and spillover of WNV to incidental hosts based on host-vector contact rates on various land cover types and over four seasons. We evaluated the relative importance of the mechanisms tested using two independent serological datasets of WNV antibodies collected in wild birds and horses. We found that the same transmission processes (seasonal virus introduction by migratory birds, Culex modestus mosquitoes as amplifying vectors, heterogeneity in avian host competence, absence of 'dilution effect') best explain the spatial variations in WNV seroprevalence in the two serological datasets. Our results provide new insights on the pathways of WNV introduction, amplification and spillover and the contribution of bird and mosquito species to WNV transmission in Southern France.

Control of lice infestation in horses using a 10 mg/mL deltamethrin topical application.

BACKGROUND: Two open-controlled studies evaluated the tolerance and the efficacy of a 10 mg/mL deltamethrin-based pour-on solution (Deltanil®; Virbac, France) in treating (study 1) and preventing (study 2) natural Damalinia equi infestations in horses. In study 1, seven adult horses received 10 mL of the solution from mane to tail head on day 0 (D0). Four adult horses, living separately, served as non-treated controls. All were naturally infected. Lice burden was recorded by counting the number of live parasites, bilaterally, over seven anatomic regions. Lesional score was based on alopecia, crusts, papules/pustules, nodules/plaques, scales and wounds, each assessed on a 0-3 scale. Evaluation was performed on D0 and subsequently weekly until D56 in treated horses and on D0 and D56 in control horses. In study 2, six adult horses free of parasites were similarly treated on D-2 and D30. Two adult horses, naturally infested with D. equi and left untreated, were mixed with the treated horses from D0 to D60. Evaluation was performed similarly to study 1 on all horses, fortnightly until D60. RESULTS: No adverse event was recorded in either study. In study 1, parasite and lesional scores of control horses were maintained on D56. Parasite scores of the treated horses were reduced by 98% on D7 and 100% from D15 to D56 (mean [SD]: D0 44 [58.4]). Lesional score in treated horses was reduced by 24, 82, 47, 91, 96, 93, 93 and 100% on D7, 15, 21, 28, 35, 42, 50 and 56, respectively (mean [SD]: D0 3.1 [1.8]). In study 2, the lice populations remained high in the two control horses throughout the study (max mean [SD]: D0 159 [151.3], min D45 34 [39.6]). On treated animals, all parasite counts were negative except on D15 (one louse found). The protection rate was 99.7% on D15 and 100% from D30 to D60. CONCLUSIONS: A single application of the 10 mg/mL deltamethrin preparation was effective and safe in the treatment and in the prevention of lice infestation in these horses. It was also effective in preventing new infestations for one month.

Strong evidence for the presence of the tick Hyalomma marginatum Koch, 1844 in southern continental France.

Hyalomma ticks can transmit several human and animal pathogens in Eurasia and Africa. Interest in Hyalomma marginatum has increased since the recent (re)emergence of Crimean-Congo Hemorrhagic fever in the Palearctic region. Until now, continental France has been considered free of this tick species. Nevertheless, the existence of incomplete and occasionally incorrect records has maintained confusion about its status. Based on several tick sampling campaigns conducted on horses and birds from 2007 to 2016, we provided very strong evidence for the presence of reproducing populations of H. marginatum in parts of southern continental France. We also confirmed the introduction of immature developmental stages of H. marginatum, as well as H. rufipes, into France probably through trans-Mediterranean bird migrations.

Piroplasmosis in an endemic area: analysis of the risk factors and their implications in the control of Theileriosis and Babesiosis in horses.

Theileria equi (Laveran 1901) and Babesia caballi (Nuttall and Strickland 1910) are the causative agents of Equine Piroplasmosis (EP), a severe and problematic disease compromising international movement of horses. Infected horses usually become asymptomatic carriers and, for this reason, their movement across borders may become restricted. The aim of this study was to assess the seroprevalence of EP in Southern France and to evaluate risk factors associated with these parasites. In 2002, we performed a complement fixation test (CF) with blood samples from 443 horses stabled at 95 different farms located in the region of Camargue. Two epidemiological questionnaires have been used: one for each single horse (individual and management factors) and one for each place where horses were sampled (environment, presence of other species, etc.) to identify risk factors for seropositivity. T. equi and B. caballi had a seroprevalence of 58 % and 12.9%, respectively. For T. equi, sex, age, activity, management, and living with or near cattle were identified as risk factors, while for B. caballi, only living in wetlands was recognized as a risk factor in the bivariate analysis. In the multivariate analysis, the best model for T. equi included as variables age, breed, and deworming, while the best model for B. caballi included the type of housing during day and the contact with cows.

Importance of wetlands management for West Nile Virus circulation risk, Camargue, Southern France.

To assess environmental and horse-level risk factors associated with West Nile Virus (WNV) circulation in Camargue, Southern France, a serosurvey was conducted on non-vaccinated horses (n = 1159 from 134 stables) in 2007 and 2008. Fifteen Landsat images were examined to quantify areas with open water and flooded vegetation around sampled horses. Mean percentages of areas of open water and flooded vegetation, as well as variations in these percentages between 3 periods (November to February = NOT, March to July = END and August to October = EPI), were calculated for buffers of 2 km radius around the stables. Results of the final logistic regression showed that the risk of WNV seropositivity in horses decreased with their date of acquisition and age. Results also demonstrated the significant role of environmental variables. Horse serological status was associated with variations of open water areas between the NOT (November to February) and END (March to July) periods, as well as between END and EPI (August to October). WNV spillover was found more intense in areas where water level decreased strongly from winter to spring and from spring to summer.