Novel tools for the diagnosis and differentiation of acute and chronic bovine besnoitiosis

Seroprevalence and Factors Associated with Toxoplasma gondii, Neospora caninum, and Besnoitia besnoiti Infections in Cattle and Goats in Selangor, Malaysia

Apicomplexan parasites such as Toxoplasma gondii, Neospora caninum, and Besnoitia besnoiti are widely recognized as causes of production diseases in ruminants. This study aimed to investigate the serological occurrence of T. gondii, N. caninum, and B. besnoiti in cattle and goats from smallholder farms in Selangor, Malaysia. A cross-sectional study was conducted on 19 farms by collecting 404 bovine (n = 225) and caprine (n = 179) serum samples, which were then essayed for T. gondii, N. caninum, and B. besnoiti antibodies using commercially available ELISA test kits. Farm data and animal characteristics were documented, and the data were analyzed using descriptive statistics and logistic regression models. The seroprevalence of T. gondii at animal and farm levels in cattle was 5.3% (95% CI 1.2-7.4%) and 36.8% (95% CI 22.4-58.0%), respectively. Animal-level seropositivity for N. caninum was 2.7% (95% CI 0.4-4.2%) and 5.7% for B. besnoiti (95% CI 1.3-9.4%) with corresponding farm-level seropositivity of 21.0% and 31.5%, respectively. For the goat samples, a high animal- (69.8%; 95% CI 34.1-82.0%) and farm-level (92.3%) seropositivity was recorded for T. gondii, but was relatively lower for N. caninum antibodies, at 3.9% (95% CI 1.5-6.2%) and 38.4% (5/13). The factors associated with T. gondii seropositivity were older animals (above 12 months) (OR = 5.3; 95% CI 1.7-16.6), semi-intensive farms (OR = 2.2; 95% CI 1.3-6.2), the presence of either dogs or cats (OR = 3.6; 95% CI 1.1-12.3), a large herd size (>100 animals) (OR = 3.7; 95% CI 1.4-10.0), and a single source of replacement animals (OR = 3.9; 95% CI 1.6-9.6). These findings are vital in developing effective control measures against these parasites in ruminant farms in Selangor, Malaysia. More national epidemiological research is required to elucidate the spatial distribution of these infections and their potential impact on Malaysia's livestock industry.

Validation of a commercial version of a competitive enzyme linked immunosorbent assay for the detection of antibodies to Besnoitia besnoiti

BACKGROUND

Several reports suggest a further spread of besnoitiosis to countries in which Besnoitia besnoiti-infected bovine herds have not been noticed yet. Cattle infected without clinical signs may represent reservoirs. Serological analyses in affected herds or animals from endemic regions are necessary to identify subclinical or inapparent infections and stop transmission to naïve animals or herds. The Monoscreen AbELISA Besnoitia besnoiti (BIO K 466) is based on a previously published in-house competitive ELISA, the Bb-cELISA1, but has a different test architecture. The present study aimed to use sera from a previous evaluation of Bb-cELISA1 to assess whether BIO K466 shows identical results. In addition, further well-characterized positive and negative samples were analysed to estimate diagnostic sensitivity and specificity.

METHODS

A first set of sera consisted of a total of 305 bovine sera, collected from German herds infected by B. besnoiti, Neospora caninum or Sarcocystis spp. Sera had been characterized by reference serological tests (i.e. immunoblot, immunofluorescence antibody test and an in-house indirect ELISA). A second set consisted of 200 confirmed B. besnoiti-positive sera from French herds. Negative cattle sera (n = 624) originated from Norway and The Netherlands, countries in which bovine besnoitiosis has not been reported yet.

RESULTS

Using the first set of sera, the BIO K466 showed an estimated diagnostic sensitivity of 97.9% (95% CI: 91.9%-99.6) and a diagnostic specificity of 99.5% (95% CI: 96.9%-100%) relative to reference serological tests. A direct comparison of the results revealed an almost perfect agreement between the results of the in-house Bb-cELISA1 and the commercialized version (kappa 0.98; 95% CI: 0.95-1). The validation using positive bovine sera from France and negative sera from other European countries revealed a diagnostic sensitivity of 97.5% (95% CI: 93.9%-99.1%) and specificity of 99.5% (95% CI: 98.5%-99.9%).

CONCLUSION

In conclusion, BIO K 466 appears to be a suitable tool to diagnose bovine besnoitiosis, but needs further validation especially in cases of inconclusive, suspected false-positive or -negative results in other serological tests.

Identification of molecular biomarkers associated with disease progression in the testis of bulls infected with Besnoitia besnoiti

Breeding bulls infected with Besnoitia besnoiti may develop sterility during either acute or chronic infection. The aim of this study was to investigate the molecular pathogenesis of B. besnoiti infection with prognosis value in bull sterility. Accordingly, five well-characterized groups of naturally and experimentally infected males were selected for the study based on clinical signs and lesions compatible with B. besnoiti infection, serological results and parasite detection. A broad panel of molecular markers representative of endothelial activation and fibrosis was investigated and complemented with a histopathological approach that included conventional histology and immunohistochemistry. The results indicated the predominance of an intense inflammatory infiltrate composed mainly of resident and recruited circulating macrophages and to a lesser extent of CD3+ cells in infected bulls. In addition, a few biomarkers were associated with acute, chronic or subclinical bovine besnoitiosis. The testicular parenchyma showed a higher number of differentially expressed genes in natural infections (acute and chronic infections) versus scrotal skin in experimental infections (subclinical infection). In subclinical infections, most genes were downregulated except for the CCL24 and CXCL2 genes, which were upregulated. In contrast, the acute phase was mainly characterized by the upregulation of IL-1α, IL-6 and TIMP1, whereas in the chronic phase, the upregulation of ICAM and the downregulation of MMP13, PLAT and IL-1α were the most relevant findings. Macrophages could be responsible for the highest level of gene regulation in the testicular parenchyma of severely affected and sterile bulls, and all these genes could be prognostic markers of sterility.

First highly sensitive and specific competitive ELISA for detection of bovine besnoitiosis with potential as a multi-species test

Serological cross-reactions represent a serious problem in some currently available tests to diagnose Besnoitia infections in many species including cattle, caribou and donkeys. False-positive results are due to the low positive-predictive value of these serological tests for besnoitiosis. These tests therefore have clear limitations if large herds are screened in areas with low prevalence, since increased numbers of false-positive reactions require confirmatory testing by alternative serological methods, e.g. immunoblotting, which are time-consuming and create extra costs. To overcome this problem, we aimed to develop a highly sensitive and specific competitive ELISA (cELISA) using a panel of 12 monoclonal antibodies raised against the tachyzoite stage of Besnoitia besnoiti. A cELISA set up with one of these antibodies (Bb-cELISA1) was screened with a large panel of B. besnoiti-positive bovine sera to estimate the diagnostic sensitivity of the test. Sera from herds with Neospora caninum- or Sarcocystis spp.-infected cattle were used to estimate its diagnostic specificity. Relative to a reference standard, which combined the results obtained in a previously established highly sensitive and specific ELISA, in the immunofluorescence antibody test and in B. besnoiti tachyzoite and bradyzoite immunoblots, the new Bb-cELISA1 revealed a diagnostic sensitivity of 99.2% (95% confidence interval: 97.1-99.9%) and a diagnostic specificity of 99.9% (95% confidence interval: 97.7-100%). This novel assay was tested on a variety of proven Besnoitia-positive sera from other species, including B. besnoiti-infected cats, rabbits or Besnoitia bennetti-infected donkeys or Besnoitia tarandi-infected caribou. The results obtained with the new Besnoitia-cELISA for these animal species also corresponded almost perfectly with those of the reference tests, which included immunoblot and immunofluorescence antibody tests. In conclusion, the novel Besnoitia-cELISA represents a valuable tool for the diagnosis and control of bovine besnoitiosis and for studies on the epidemiology of Besnoitia infections in a variety of host species, including naturally exposed wildlife and experimental hosts.

Vascular wall injury and inflammation are key pathogenic mechanisms responsible for early testicular degeneration during acute besnoitiosis in bulls

Background

Bovine besnoitiosis, caused by the apicomplexan parasite Besnoitia besnoiti, is a chronic and debilitating cattle disease that notably impairs fertility. Acutely infected bulls may develop respiratory signs and orchitis, and sterility has been reported in chronic infections. However, the pathogenesis of acute disease and its impact on reproductive function remain unknown.

Methods

Herein, we studied the microscopic lesions as well as parasite presence and load in the testis (pampiniform plexus, testicular parenchyma and scrotal skin) of seven bulls with an acute B. besnoiti infection. Acute infection was confirmed by serological techniques (IgM seropositive results and IgG seronegative results) and subsequent parasite detection by PCR and histological techniques.

Results

The most parasitized tissue was the scrotal skin. Moreover, the presence of tachyzoites, as shown by immunohistochemistry, was associated with vasculitis, and three bulls had already developed juvenile tissue cysts. In all animals, severe endothelial injury was evidenced by marked congestion, thrombosis, necrotizing vasculitis and angiogenesis, among others, in the pampiniform plexus, testicular parenchyma and scrotal skin. Vascular lesions coexisted with lesions characteristic of a chronic infection in the majority of bulls: hyperkeratosis, acanthosis and a marked diffuse fibroplasia in the dermis of the scrotum. An intense inflammatory infiltrate was also observed in the testicular parenchyma accompanied by different degrees of germline atrophy in the seminiferous tubules with the disappearance of various strata of germ cells in four bulls.

Conclusions

This study confirmed that severe acute besnoitiosis leads to early sterility that might be permanent, which is supported by the severe lesions observed. Consequently, we hypothesized that testicular degeneration might be a consequence of (i) thermoregulation failure induced by vascular lesions in pampiniform plexus and scrotal skin lesions; (ii) severe vascular wall injury induced by the inflammatory response in the testis; and (iii) blood-testis barrier damage and alteration of spermatogenesis by immunoresponse.

Sensitive, quantitative detection of Besnoitia darlingi and related parasites in intermediate hosts and to assess felids as definitive hosts for known and as-yet undescribed related parasite species

Besnoitia darlingi, B. neotomofelis and B. oryctofelisi are closely related coccidian parasites with cats as definitive hosts. While B. darlingi uses opossums as intermediate hosts, B. neotomofelis and B. oryctofelisi have been described in Southern Plains woodrats (Neotoma micropus) from the USA and in domestic rabbits from Argentina, respectively. A comparison of the Internal Transcribed Spacer-1 (ITS-1) region of the ribosomal DNA (rDNA) of these Besnoitia spp. showed only a few differences. The present study aimed at developing a real-time PCR to detect B. darlingi, B. neotomofelis and B. oryctofelisi in tissues of intermediate and in faeces of definitive hosts in order to support studies of these organisms’ epidemiology and pathogenesis.

The established PCR was based on primer regions distinct from the ITS-1 sequences of ungulate Besnoitia spp. and made use of a Besnoitia universal probe. To monitor inhibition, a heterologous internal control was established based on the enhanced green fluorescent protein gene. The real-time PCR reacted with B. darlingi, B. neotomofelis and B. oryctofelisi, while the novel PCR did not recognize ungulate Besnoitia spp. (B. besnoiti, B. bennetti, B. tarandi). DNA of Apicomplexa ascribed to other Besnoitia-related genera, including other gut parasites of cats (Cryptosporidium parvum, Giardia duodenalis, Tritrichomonas foetus), was not recognized. The real-time PCR had an analytic sensitivity of less than 1 tachyzoite per reaction. In feline faeces spiked with B. darlingi oocysts, the limit of detection was a DNA amount equivalent to 1 oocyst per PCR reaction. In B. darlingi infected ɣ-interferon knock-out mice, the lung was identified as the predilection organ. In conclusion, this real-time PCR should advance further studies on these parasites and may inspire research on related species, not only in the Americas, but also in other parts of the world.

•

A quantitative real-time PCR was established to detect Besnoitia darlingi.

•

Analytical sensitivity of the real-time PCR for tachyzoites and oocysts was high.

•

Lung tissue was the predilection site for B. darlingi in ɣ-interferon knockout mice.

•

Related parasites like B. neotomofelis and B. oryctofelisi are detected by this PCR, too.

•

PCR holds promise to assess the epidemiology of B. darlingi and related species.

Species-specific differences in Toxoplasma gondii, Neospora caninum and Besnoitia besnoiti seroprevalence in Namibian wildlife

Background

Knowledge about parasitic infections is crucial information for animal health, particularly of free-ranging species that might come into contact with livestock and humans.

Methods

We investigated the seroprevalence of three tissue-cyst-forming apicomplexan parasites (Toxoplasma gondii, Neospora caninum and Besnoitia besnoiti) in 506 individuals of 12 wildlife species in Namibia using in-house enzyme linked immunosorbent assays (indirect ELISAs applying purified antigens) for screening and immunoblots as confirmatory tests. We included six species of the suborder Feliformia, four species of the suborder Caniformia and two species of the suborder Ruminantia. For the two species for which we had most samples and life-history information, i.e. cheetahs (Acinonyx jubatus, n = 250) and leopards (Panthera pardus, n = 58), we investigated T. gondii seroprevalence in relation to age class, sex, sociality (solitary, mother-offspring group, independent sibling group, coalition group) and site (natural habitat vs farmland).

Results

All but one carnivore species (bat-eared fox Otocyon megalotis, n = 4) were seropositive to T. gondii, with a seroprevalence ranging from 52.4% (131/250) in cheetahs to 93.2% (55/59) in African lions (Panthera leo). We also detected antibodies to T. gondii in 10.0% (2/20) of blue wildebeest (Connochaetes taurinus). Adult cheetahs and leopards were more likely to be seropositive to T. gondii than subadult conspecifics, whereas seroprevalence did not vary with sex, sociality and site. Furthermore, we measured antibodies to N. caninum in 15.4% (2/13) of brown hyenas (Hyaena brunnea) and 2.6% (1/39) of black-backed jackals (Canis mesomelas). Antibodies to B. besnoiti were detected in 3.4% (2/59) of African lions and 20.0% (4/20) of blue wildebeest.

Conclusions

Our results demonstrate that Namibian wildlife species were exposed to apicomplexan parasites at different prevalences, depending on parasite and host species. In addition to serological work, molecular work is also needed to better understand the sylvatic cycle and the clear role of wildlife in the epidemiology of these parasites in southern Africa.

Added value of IgM detection and low avidity index as markers of acute bovine besnoitiosis

Early in vivo diagnosis of bovine besnoitiosis is crucial for the success of control programmes. However, diagnosis in acutely infected animals is hindered by the low sensitivity of the available serological tools. In this study, a novel ELISA to detect specific anti-Besnoitia besnoiti IgM antibodies was developed. The usefulness of this tool together with an avidity ELISA were studied with a well-coded sera panel from experimentally and naturally infected cattle. First, the kinetics of specific IgM levels were determined in experimentally infected calves during the acute and chronic infection. Next, IgM levels were determined in naturally infected cattle with either acute or chronic infection. Finally, the IgG avidity index was monitored in both experimentally and naturally infected cattle. Specific IgM antibodies were detected prior to specific IgG antibodies (7-19 days vs. 17-26 days post-infection). A prompt IgM response was associated with the end of the febrile stage in experimentally infected calves. Naturally and experimentally infected animals with acute clinical signs tested IgM-positive but IgG-negative, followed by IgG seroconversion 2-3 weeks later. Chronically infected cattle developed both IgM and IgG specific antibodies. Moreover, a progressive increase in the avidity index (AI) was observed in all experimentally infected calves during the course of the experimental trials. However, a low AI coincided with visible tissue cysts. Low avidity values were also detected when naturally infected cattle with acute clinical signs seroconverted, in contrast to a high AI detected in chronically infected cattle. In summary, IgM and avidity ELISAs improved the early in vivo diagnosis of bovine besnoitiosis. IgM-positive but IgG-negative results were indicative of an acute infection, whereas IgG positive results accompanied by low avidity values confirmed a recent infection.

Besnoitia besnoiti seroprevalence in beef, dairy and bullfighting cattle in Catalonia (north-eastern Spain): A cross-sectional study

Besnoitia besnoiti is the causative agent of bovine besnoitiosis, a chronic and debilitating disease of cattle that recently re-emerged and seems to be spreading in Europe. A cross-sectional serological study was carried out in different cattle herds in Catalonia, north-eastern Spain, to determine the seroprevalence of B. besnoiti in the region. A total of 791 serum samples (beef cattle n = 338, dairy cattle n = 291; bullfighting cattle n = 162) were tested. Sera were first screened for antibodies against Besnoitia using a commercial Enzyme-Linked Immunosorbent Assay (ELISA) applying a cut-off that was lower than that recommended by the manufacturer in order to reach highest sensitivity. Sera above the chosen cut-off of 15% positivity (PP) were further tested by the Indirect Fluorescent Antibody Test (IFAT) and respectively positive results were confirmed by a B. besnoiti tachyzoite-based immunoblot. A total of 504/791 (63.7%) sera showed ELISA values above the selected cut-off, and 91 of these samples also yielded positive results in IFAT (cut-off titre 1:200). By immunoblot, a positive result was obtained in 93.4% (85 out of the 91) of the IFAT-positive samples. Interestingly, all confirmed Besnoitia-seropositive cases corresponded exclusively to beef cattle from the Pyrenees area, resulting in a prevalence of 25.1% (85/338) at the animal level and of 46% (36/78) at the herd level in this cattle group. No specific antibodies against Besnoitia could be detected in dairy and bullfighting cattle. The obtained results suggested that Besnoitia infections are present in Catalonia, consequently, diagnosis of this parasitic infection should be included in the sanitary control and before trading and movement of animals.

Besnoitia tarandi in Canadian woodland caribou - Isolation, characterization and suitability for serological tests

In the present study, we report the first in vitro isolation of Besnoitia tarandi from North America and the second of B. tarandi at all. The parasite was isolated directly from the skin of a Canadian woodland caribou from the migratory ecotype. The animal belonged to the Leaf River Herd, in Northern Quebec, Canada. The isolate was designated Bt-CA-Quebec1.

Sequencing of the 3’-end of the 18S rRNA gene, the complete sequence of the ITS1 and the 5’-end of the 5.8S rRNA gene of Bt-CA-Quebec1 revealed only minor differences to rDNA gene fragments of B. besnoiti. In contrast, the patterns for the microsatellite loci Bt-20 and Bt-21 varied substantially from those reported for B. besnoiti and B. bennetti. Surprisingly, the typing results in the loci Bt-6 and Bt-7 differed between Bt-CA-Quebec1 and results obtained for skin samples from caribou of the Canadian regions of Nunavut and the Northwest Territories reported by other investigators. This indicates that differences might exist among B. tarandi in caribou from different regions in Canada.

Mice (γ-interferon knockout) intraperitoneally inoculated with 1.2 × 10⁶ or 1.5 × 10⁶ bradyzoites mechanically released from skin tissue cysts fell ill 8, 9 or 18 days post inoculation. GKO mice inoculated with 3.0 × 10⁴ tachyzoites isolated from the peritoneal cavity of a bradyzoites-inoculated mouse became ill earlier, i.e. 5 days post inoculation. Lung was the predilection site in all mice.

Bt-CA-Quebec1 tachyzoites rapidly grew in MARC-145 cells and were used for antigen production. Comparative Western blot analyses revealed only a few differences between B. tarandi Bt-CA-Quebec1 and B. besnoiti Evora antigen when probed with sera collected from chronically infected caribou.

Due to its fast growth in vitro, the Bt-CA-Quebec1 isolate may represent an interesting antigen source to establish B. tarandi-specific serological tools and to study the biology of this parasite species further.

•

Besnoitia tarandi was in vitro-isolated directly from the skin of a Canadian woodland caribou.

•

Microsatellite typing revealed differences to existing Bt-6, Bt-7 and Bt-21 patterns of B. tarandi.

•

The isolate Bt-CA-Quebec1 caused disease in γ-interferon knockout mice.

•

Bt-CA-Quebec1 rapidly grows in MARC-145 cells.

•

Antigens of Bt-CA-Quebec1 are similar but not identical to those of Besnoitia besnoiti.

Development and characterization of monoclonal antibodies againstBesnoitia besnoititachyzoites

This is the first report on the development and characterization of eight monoclonal antibodies (MABs) generated against whole- and membrane-enriched tachyzoite extracts of the apicomplexan parasiteBesnoitia besnoiti. Confocal laser scanning immunofluorescence microscopy was used to localize respective epitopes inB. besnoititachyzoites along the lytic cycle. A pattern compatible with dense granule staining was observed with MABs 2.A.12, 2.F.3 and 2.G.4, which could be confirmed by immunogold electron microscopy for MABs 2.A.12 and 2.F.3. In particular, MABs 2.F.3 and 2.G.4 were secreted during early invasion, proliferation and egress phases. MABs 3.10.8 and 5.5.11 labelled the tachyzoite surface, whilst MABs 1.17.8, 8.9.2 and 2.G.A recognized the apical tip, which is reminiscent for microneme localization. Besides, the epitopes recognized by the latter two (MABs 8.9.2 and 2.G.A) exhibited a redistribution from the anterior part across the parasite surface towards the posterior end during invasion. Most MABs developed were genus-specific. Indeed, the MABs cross-reacted neither withT. gondiinor withN. caninumtachyzoites. In summary, we have generated MABs that will be useful to study the key processes in the lytic cycle of the parasite and with additional promising diagnostic value. However, the molecular identity of the antigens recognized remains to be elucidated.

Naturally acquired bovine besnoitiosis: Disease frequency, risk and outcome in an endemically infected beef herd

The recent spread of bovine besnoitiosis warrants further epidemiological investigations to improve the knowledge on disease development. Thus, a 4-year longitudinal open cohort study was conducted in the first German cattle herd naturally infected with Besnoitia besnoiti. At seven herd-visits between 2008 and 2012, fourteen breeding bulls (>1.5 years) and 131 females (>1 year) were examined clinically and serologically. In females, clinical and serological prevalences, incidence and remission rates were determined. In addition, the association of age, antibody levels and number of visible parasitic cysts with clinical and serological outcome was investigated. The seroprevalence (89.4%-100%) and serological incidence rate (140.5 per 100 animal-years) were considerably higher than the clinical prevalence (23.5%-36.6%) and clinical incidence rate (16.7 per 100 animal-years). Of 33 new clinical and 12 new serological cases, only 6.7% (3/45) attracted attention with clinical signs of acute bovine besnoitiosis. The apparent serological remission rate (1.9 per 100 animal-years) was considerably lower than the clinical remission rate (37.3 per 100 animal-years). A median cyst score of <1 and mean immunofluorescent antibody test (IFAT) titre of ≤1,600 over the entire observation period was significantly associated with a negative clinical outcome at the end. Overall cyst score was not significantly associated with serological outcome and age had no significant influence on clinical and serological outcome. Within 4 years, there was a significant reduction in cyst scores and IFAT titres in the same animals, leading to eight clinically and serologically negative animals in the end. Two initially negative animals achieved clinical and apparent serological remission in about 2.5 years. In bulls, the time between herd entry and seroconversion was 7-30 months and the serological incidence rate was nearly identical to the rate in females (142.0 per 100 animal-years). This shows that a high B. besnoiti prevalence leads to infection of bulls within a short time period.

Bovine chronic besnoitiosis in a calf: Characterization of a novel B. besnoiti isolate from an unusual case report

Bovine besnoitiosis, caused by the apicomplexan Besnoitia besnoiti, is a chronic and debilitating disease characterized by cutaneous and systemic manifestations that primarily affects adult beef cattle. Previous studies have reported that clinical besnoitiosisis is rare in calves. However, we isolated B. besnoiti from a chronically infected calf for the first time. The identity of the Besnoitia species was determined after parasite isolation and molecular genotyping. According to the results obtained in vitro the new isolate, named as Bb-Spain3, was characterized in a reproducible in vitro model and was categorized as a low invader and low prolific isolate with a slower lytic cycle compared to Bb-Spain 1 isolate. Specific traits that differentiate isolates obtained from adult animals from those infecting calves were not found. Next, we described the first case report of chronic besnoitiosis in a female calf less than 6 months-old with a low body condition. The disease was confirmed by the presence of specific anti-B. besnoiti antibodies and parasite detection in the skin. At post-mortem examination, tissue samples were collected for histological, immunohistochemical and molecular analyses. DNA-parasite was detected in 31 different calf's tissues, being the most highly parasitized tissues the skin and the respiratory and reproductive tracts. In addition, the parasite was also present in heart, eyes, lymph nodes and brain. The high parasite load, a wide intra-organic parasite distribution and the presence of both viable and degenerated cysts, were indicative of a rapid progression of the disease. This case report underlines the need to include the inspection of young animals in besnoitiosis control.

Advances in the diagnosis of bovine besnoitiosis: current options and applications for control

Bovine besnoitiosis, which is caused by the tissue cyst-forming intracellular parasite Besnoitia besnoiti, is a chronic and debilitating disease that is responsible for severe economic losses in the cattle raised under extensive husbandry systems. The absence of vaccines, treatments or a health scheme at local, national and international levels has led to a rapid spread of bovine besnoitiosis from western Europe towards eastern countries and northwards. Moreover, this parasitic disease is widely present in many sub-Saharan countries. Thus, bovine besnoitiosis should be included in the animal health scheme of beef cattle herds. Accurate diagnostic tools and common diagnostic procedures are mandatory in any control programme. Relevant advances have been made in this field during the last decade. Succeeding with accurate diagnosis relies on the technique employed and the antibody and parasite kinetics of the infection stage, which may notably influence control programmes and surveillance. Moreover, control programmes should be adapted to the epidemiological status of the disease, as the disease presentation in a herd has important implications for prospective control. Herein, we review the clinical disease presentation of bovine besnoitiosis and the correlation between its clinical course and laboratory parameters. We also provide an update on the available diagnostic tools, discuss their strengths and pitfalls, and provide guidelines for their use in control, surveillance and epidemiological studies. A rational control strategy is also recommended.

A new lyophilized tachyzoite based ELISA to diagnose Besnoitia spp. infection in bovids and wild ruminants improves specificity

Recent studies have reported that routinely used whole or soluble Besnoitia besnoiti tachyzoite (TZ) extract-based ELISAs potentially give rise to a high number of false-positive results, which may compromise control and the epidemiological studies of bovine besnoitiosis. Thus, western blot (WB) has been recommended as a confirmatory test. In the present study, a new ELISA test that employs lyophilized tachyzoites for the first time (BbSALUVET ELISA 2.0) was developed and validated with cattle sera (n=606) under a worst-case scenario. False positive and false negative, soluble TZ extract-based BbSALUVET ELISA 1.0 reactors were overrepresented, and WB was used as the reference test. One commercial test (PrioCHECK Besnoitia Ab 2.0, which employs whole TZ extract) and a recently developed membrane-enriched ELISA (APure-BbELISA) were also tested. The three ELISAs showed high AUC values (>0.9). However, the best diagnostic performance corresponded to the BbSALUVET ELISA 2.0 and the APure-BbELISA [(92% sensitivity (Se) and 98% specificity (Sp)] followed by PrioCHECK Besnoitia Ab 2.0 (88% Se, 98% Sp, and 4.5% doubtful results). In addition, the BbSALUVET ELISA 2.0 was validated with wild ruminant sera, and excellent performance (96% Se, 97% Sp, and 4% doubtful results) was obtained again. A different antigenic composition of the lyophilized tachyzoites, compared with whole or soluble tachyzoite extracts, may be responsible for the improved diagnostic performance. This study proposes the use of the BbSALUVET ELISA 2.0 in cattle prior to entry to herds free of the disease and in valuable samples prior to a selective culling without the need of a confirmatory Western Blot test in positive samples due to its excellent specificity.

A serosurvey of selected cystogenic coccidia in Spanish equids: first detection of anti-Besnoitia spp. specific antibodies in Europe

Background

Equine besnoitiosis, caused by Besnoitia bennetti, and equine protozoal myeloencephalitis (EPM), caused by Sarcocystis neurona and Neospora hughesi are relevant equine diseases in the Americas that have been scarcely studied in Europe. Thus, a serosurvey of these cystogenic coccidia was carried out in Southern Spain. A cross-sectional study was performed and serum samples from horses (n = 553), donkeys (n = 85) and mules (n = 83) were included. An in-house enzyme-linked immunosorbent assay (ELISA) was employed to identify a Besnoitia spp. infection and positive results were confirmed by an a posteriori western blot. For Neospora spp. and Sarcocystis spp., infections were detected using in-house ELISAs based on the parasite surface antigens N. hughesi rNhSAG1 and S. neurona rSnSAG2/3/4. Risk factors associated with these protozoan infections were also investigated.

Results

Antibodies against Besnoitia spp., Neospora spp. and Sarcocystis spp. infections were detected in 51 (7.1%), 46 (6.4%) and 20 (2.8%) of 721 equids, respectively. The principal risk factors associated with a higher seroprevalence of Besnoitia spp. were the host species (mule or donkey), the absence of shelter and the absence of a rodent control programme. The presence of rodents was the only risk factor for Neospora spp. infection.

Conclusions

This study was the first extensive serosurvey of Besnoitia spp. infection in European equids accomplished by two complementary tests and gives evidence of the presence of specific antibodies in these populations. However, the origin of the infection is still unclear. Further parasite detection and molecular genotyping are needed to identify the causative Besnoitia and Neospora species. Finally, cross-reactions with antibodies directed against other species of Sarcocystis might explain the positive reactions against the S. neurona antigens.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-1046-z) contains supplementary material, which is available to authorized users.

Importance of serological cross-reactivity among Toxoplasma gondii, Hammondia spp., Neospora spp., Sarcocystis spp. and Besnoitia besnoiti

Toxoplasma gondii, Neospora spp., Sarcocystis spp., Hammondia spp. and Besnoitia besnoiti are genetically related cyst-forming coccidia. Serology is frequently used for the identification of T. gondii, Neospora spp. and B. besnoiti-exposed individuals. Serologic cross-reactions occur in different tests among animals infected with T. gondii and H. hammondi, as well as among animals infected by T. gondii and N. caninum. Infections caused by N. caninum and N. hughesi are almost indistinguishable by serology. Neospora caninum, B. besnoiti and Sarcocystis spp. infections in cattle show some degree of serologic cross-reactivity. Antibody cross-reactivity between Neospora spp. and H. heydorni-infected animals is suspected, but not proven to occur. We review serologic cross-reactivity among animals and/or humans infected with T. gondii, Neospora spp., Sarcocystis spp., Hammondia spp. and B. besnoiti. Emphasis is laid upon antigens and serological methods for N. caninum diagnosis which were tested for cross-reactivity with related protozoa. Species-specific antigens, as well as stage-specific proteins have been identified in some of these parasites and have promising use for diagnosis and epidemiological surveys.

Far beyond Phagocytosis: Phagocyte-Derived Extracellular Traps Act Efficiently against Protozoan Parasites In Vitro and In Vivo

Professional mononuclear phagocytes such as polymorphonuclear neutrophils (PMN), monocytes, and macrophages are considered as the first line of defence against invasive pathogens. The formation of extracellular traps (ETs) by activated mononuclear phagocytes is meanwhile well accepted as an effector mechanism of the early host innate immune response acting against microbial infections. Recent investigations showed evidence that ETosis is a widely spread effector mechanism in vertebrates and invertebrates being utilized to entrap and kill bacteria, fungi, viruses, and protozoan parasites. ETs are released in response to intact protozoan parasites or to parasite-specific antigens in a controlled cell death process. Released ETs consist of nuclear DNA as backbone adorned with histones, antimicrobial peptides, and phagocyte-specific granular enzymes thereby producing a sticky extracellular matrix capable of entrapping and killing pathogens. This review summarizes recent data on protozoa-induced ETosis. Special attention will be given to molecular mechanisms of protozoa-induced ETosis and on its consequences for the parasites successful reproduction and life cycle accomplishment.

Naturally acquired bovine besnoitiosis: Differential distribution of parasites in the skin of chronically infected cattle

Bovine besnoitiosis is caused by Besnoitia besnoiti, an apicomplexan parasite closely related to Toxoplasma gondii and Neospora caninum. In the acute stage of besnoitiosis, cattle suffer from pyrexia, swollen lymph nodes, anorexia and subcutaneous edema. In the chronic stage, tissue cysts are formed in a variety of tissues including the skin. Knowledge about the distribution of tissue cysts of different parts of the skin of infected animals is scarce. Four chronically infected cattle were euthanized and skin samples were taken from a total of 77 standardized cutaneous locations per animal. Portions of the dermis were taken, from which DNA was extracted and examined by real-time PCR. Cycle of transition (Ct) values reflecting the amount of parasite DNA in the samples were determined. For statistical analysis, samples were attributed to 11 larger skin regions ('OuterHindlegDistal', 'Rump, ForelegMiddle', 'NoseFrontEars', 'CheekEye', 'SideLowerPart', 'ForelegDistal', 'SideUpperPart', 'LegsInner', 'VentralHeadNeck', 'DorsalNeckWithersBackTail'). While all samples revealed a positive result in three female cattle, only 63.6% (49/77) of the samples of a bull showed positive results. For statistical analysis, a Ct value of 45 was assumed for samples with a negative result. The dams showed median Ct values of 16.1, 17.5 and 19.4, while in skin samples of the bull a median Ct value of 37.6 was observed. To determine the differences in DNA concentrations between different locations of the skin of the animals, a relative Ct (relCt) was determined by subtracting for each animal indv the MedianCtindv from each sample Ct. Analyses of the relCt values showed that the highest relative parasite DNA concentrations were observed in the categories 'OuterHindlegDistal', 'Rump', 'ForelegMiddle' and 'NoseFrontEars'. The relCt values in these categories differed statistically significantly from those determined for the categories 'VentralHeadNeck' and 'DorsalNeckWithersBackTail'. The analysis showed clear differences in the distribution and the detectability of parasite DNA in the skin of cattle infected with B. besnoiti. In all four animals, samples from the 'Rump' region (Regio fermoris) showed high parasite DNA concentrations. Because this region is also easily accessible for veterinarians, this skin location appears to be optimal for taking skin biopsies for detection or isolation of B. besnoiti.

Anti-Neospora caninum and anti-Sarcocystis spp. specific antibodies cross-react with Besnoitia besnoiti and influence the serological diagnosis of bovine besnoitiosis

Bovine besnoitiosis control remains a challenge because the disease continues to spread and control relies solely on accurate diagnosis coupled to management measures. However, recent studies have reported that routinely used ELISAs may raise a high number of false-positive results. Herein, cross-reactions between Besnoitia besnoiti antigens and anti-Neospora caninum and/or anti-Sarcocystis spp.-specific antibodies were studied in an in house ELISA since N. caninum and Sarcocystis spp. are closely related parasites, and both infections are highly prevalent in cattle worldwide. The serum panel was composed of the following categories: sera from B. besnoiti-seronegative (n=75) and -seropositive cattle (n=66), B. besnoiti-based-ELISA false-positive reactors (n=96) together with N. caninum (n=36) and Sarcocystis spp. (n=42) -seropositive reference cattle sera. B. besnoiti tachyzoite based western blot (WB) results classified animals as seropositive or seronegative. Sera were analyzed for the detection of anti-N. caninum by WB and ELISA and anti-Sarcocystis spp.-specific antibodies by WB and IFAT. Those samples recognizing a Sarcocystis spp. 18-20 kDa antigenic region and N. caninum 17-18 kDa immunodominant antigen were considered to be Sarcocystis spp. and N. caninum seropositive, respectively. The category of B. besnoiti based-ELISA false-positive reactors showed the highest number of sera with specific anti-Sarcocystis spp. and anti-N. caninum antibodies (74%; 71/96), followed by the N. caninum-seropositive cattle category (52.8%; 19/36). In contrast, few B. besnoiti-seronegative and -seropositive cattle showed antibodies against Sarcocystis spp. and N. caninum (10.7%; 8/75 and 1.5%; 1/66), respectively). This study revealed that B. besnoiti false-positive ELISA results were associated not only with the presence of anti-N. caninum and anti-Sarcocystis spp. antibodies (χ(2): 78.36; p<0.0001; OR: 34.6; CI: 14-88) but also with high antibody levels against them using ELISA and IFAT tests, respectively (p<0.05; t-test). These results may explain why only some animals seropositive to Sarcocystis spp. and/or N. caninum are Besnoitia false-positive reactors. Therefore, sera meeting these requirements should be included in future validations of serological tests for bovine besnoitiosis.

Experimental infections of rabbits with proliferative and latent stages of Besnoitia besnoiti

Cattle besnoitiosis due to Besnoitia besnoiti is spreading across Europe and is responsible for severe economic losses in newly infected herds. Experimentally speaking, rabbits have been found to be susceptible to this parasite. The adaptation of B. besnoiti to rabbits may offer a new, easier and cheaper model of investigation for this disease. This study compared the virulence between tachyzoites and bradyzoites of B. besnoiti in rabbits. Eighteen New Zealand rabbits were allocated into three groups of six animals each. The rabbits from the control (group C), "tachyzoite" (group T) and "bradyzoite" (group B) groups were subcutaneously injected in the right flank with 66 μg of ovalbumin, 6.10(6) tachyzoites (125th passage on Vero cells) and 6.10(6) bradyzoites (collected from a natural infected cow) of B. besnoiti, respectively. Clinical follow-up and blood sampling for serological survey and qPCR were performed during 10 weeks until euthanasia. Molecular and immunohistochemistry examination was achieved on 25 samples of tissue per rabbit. Seroconversion occurred in group T without any clinical signs. Rabbits of group B exhibited a febrile condition (temperature above 40 °C from day 8 to day 11 following injection) with positive qPCR in blood. Cysts of B. besnoiti were found on skin samples and organs of rabbits from group B in tissue explored with threshold cycle (Ct) values below 30. These results suggest a higher virulence of bradyzoites in rabbits than Vero cell-cultivated tachyzoites. The proposed model could be used to assess the in vivo effectiveness of vaccine or drugs against cattle besnoitiosis.

Natural Besnoitia besnoiti infections in cattle: chronology of disease progression

Background

Bovine besnoitiosis is an emerging protozoan disease in cattle. Neither vaccines nor chemotherapeutic drugs are currently available for prevention and treatment of Besnoitia besnoiti infections. Therefore the implementation of appropriate disease management strategies is of utmost importance. The aim of this longitudinal study was to complement current knowledge on the chronology of disease progression. This was realized by correlating clinical findings in early stages of naturally acquired bovine besnoitiosis with results of real-time PCR of skin biopsies and of two western immunoblots and an immunofluorescent antibody test (IFAT).

Animals for this study were obtained by i) closely monitoring a cow-calf operation with a high prevalence of bovine besnoitiosis for cases of acute disease, and by ii) conducting a 12-week cohabitation experiment on pasture with five healthy heifers, a healthy bull and five B. besnoiti infected cows. A control group of six healthy heifers was kept at a minimal distance of 20 m. Further, the spectrum of potential insect vectors was determined.

Results

Infected cattle were followed up to a maximum of 221 days after first detection of B. besnoiti antibodies. Two severely affected cows developed visible and palpable alterations of skin, a decrease in body condition despite good feed intake, and chronic bovine besnoitiosis-associated laminitis leading to non-healing sole ulcers. The cows also had high reciprocal IFAT titers and high loads of parasite DNA in skin samples. Two heifers developed a mild clinical course characterized by few parasitic cysts visible in the scleral conjunctivae and vestibula vaginae. Both heifers became infected during the time of high insect activity of the species Musca domestica, Musca autumnalis, Haematobia irritans, and Stomoxys calcitrans. When a third heifer became subclinically infected, low insect activity was recorded. None of the six control heifers contracted a B. besnoiti infection.

Conclusions

In chronic besnoitiosis, the severe clinical course apparently corresponded with high reciprocal IFAT titers and high loads of parasite DNA in skin, whereas mild and subclinical cases displayed lower values. Bovine besnoitiosis-associated laminitis represents an important complication in severe chronic disease which severely impairs animal welfare.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0344-6) contains supplementary material, which is available to authorized users.

Natural Besnoitia besnoiti infections in cattle: hematological alterations and changes in serum chemistry and enzyme activities

Background

The emerging disease bovine besnoitiosis is caused by the apicomplexan parasite Besnoitia besnoiti. Clinical signs of acute besnoitiosis are pyrexia, anorexia and subcutaneous edema. In subacute and chronic besnoitiosis parasitic cysts arise in a variety of tissues and affected cattle display skin lesions and weight loss. In all stages of bovine besnoitiosis, lesions can be found in many organ systems and therefore presumably alter a variety of laboratory parameters. In this study, the impact of naturally acquired acute, subacute and chronic bovine besnoitiosis on hematologic parameters, serum chemistry, and enzyme activities was investigated. Laboratory parameters of two Simmental heifers and two Limousin cows were monitored during acute, subacute and chronic besnoitiosis and in another Simmental heifer during subclinical besnoitiosis. To determine aberrations of laboratory parameters, values were compared with reference ranges obtained from B. besnoiti negative Simmentals (224 samples of nine animals) and Limousins (41 animals). Further, laboratory parameters of B. besnoiti seropositive Limousin cows (54 animals; 32 of these showing clinical signs) and healthy B. besnoiti seronegative Limousin cows (41 animals) were compared.

Results

During acute and subacute besnoitiosis, a reduction of leukocyte and erythrocyte concentrations, hematocrit, serum albumin, urea, magnesium, and calcium concentrations were observed. Serum total protein, globulin, total bilirubin and creatinine concentrations were increased and aspartate transaminase (AST) and creatine kinase (CK) activities were elevated. In chronic besnoitiosis, erythrocyte parameters were statistically significantly lower, and total protein and globulin concentrations were significantly higher in B. besnoiti seropositive compared with B. besnoiti seronegative Limousin cows.

Conclusions

In this study, altered laboratory parameters during the course of naturally acquired acute, subacute and chronic bovine besnoitiosis are described for the first time. Only a few animals were examined in acute and subacute besnoitiosis, however the alterations of laboratory parameters during these stages reflected i) the acute inflammatory state (e.g. high levels of serum globulin fractions), ii) clinical findings such as disturbed condition (e.g. bilirubin concentrations), and iii) lesions such as muscle necroses described in the literature (e.g. AST or CK activities). Chronic besnoitiosis led to typical alterations of chronic inflammatory diseases like hyper-(gamma)-globulinemia or reduced erythrocyte concentrations.

Besnoitia besnoiti tachyzoites induce monocyte extracellular trap formation

Extracellular trap (ET) formation has been demonstrated as an important novel effector mechanism of polymorphonuclear neutrophils (PMN), eosinophils, mast cells and macrophages acting extracellularly against pathogens. In the present study, we show that tachyzoites of the emerging apicomplexan parasite Besnoitia besnoiti, that have recently been reported as potent inducers of PMN-derived ETosis, also trigger the release of ETs in an additional cell type, namely in monocytes. Fluorescence illustrations as well as scanning electron microscopy analyses (SEM) showed monocyte-promoted ET formation to be rapidly induced upon exposure to viable tachyzoites of B. besnoiti. Classical characteristics of ETs were confirmed by the co-localization of extracellular DNA with histones (H3) or myeloperoxidase (MPO) in parasite-entrapping structures. Monocyte-derived ETs were efficiently abolished by DNase I treatment and significantly reduced by treatments with inhibitors of MPO and NADPH oxidase, thus strengthening the key roles of reactive oxygen species (ROS) and MPO in monocyte ET formation. For comparative reasons, we additionally tested sporozoite stages of the closely related parasite Eimeria bovis for their capacity to induce monocyte-derived ETs and showed that these stages indeed induce ETs. To our best knowledge, we here report for the first time on monocyte ETs against the apicomplexan parasites B. besnoiti and E. bovis. Our results indicate that monocyte-triggered ETs may represent an important effector mechanism of the host early innate immune response against B. besnoiti and add a new cell type to the list of cells capable to release ETs.

Naturally acquired bovine besnoitiosis: histological and immunohistochemical findings in acute, subacute, and chronic disease

The pathogenesis of bovine besnoitiosis, a disease of increasing concern within Europe, is still incompletely understood. In this study, disease progression after natural infection with the causative apicomplexan Besnoitia besnoiti was monitored in histological skin sections of 5 individual female cattle over time. High-frequency skin sampling of 2 cattle with mild and 2 with severe acute, subacute, and chronic besnoitiosis, as well as from 1 animal during subclinical disease, enabled documentation from the beginning of the disease. Skin sections were stained with hematoxylin and eosin and Giemsa, periodic acid-Schiff reaction, and anti-Besnoitia immunohistochemistry. In all 4 clinically affected animals, tachyzoite-like endozoites could be detected for the first time by immunohistochemistry, and tissue cyst evolution was monitored. Besnoitiosis-associated lesions were not detected in the animal showing the subclinical course. Because of the inconsistency of the nomenclature of Besnoitia tissue cyst layers in the literature, a new nomenclature for B. besnoiti cyst wall layers is proposed: tissue cysts consist of a hypertrophied host cell with enlarged nuclei, an intracytoplasmic parasitophorous vacuole with bradyzoites, a sometimes vacuolated inner cyst wall, and an outer cyst wall in more developed cysts. Inner and outer cyst walls can be readily distinguished by using special stains. In 1 animal, extracystic B. besnoiti zoites were immunohistochemically detected during the chronic stage. At necropsy, the 2 severely affected cows displayed large numbers of B. besnoiti cysts in a variety of tissues, including the corium of the claws, contributing mainly to the development of chronic laminitis in these 2 cases.

Dynamics of Besnoitia besnoiti infection in cattle

Bovine besnoitiosis is caused by the cyst-forming apicomplexan parasite Besnoitia besnoiti. This disease progresses in two sequential phases: a febrile acute phase with oedemas and respiratory disorders, and a chronic phase characterized by the presence of subcutaneous tissue cysts and skin lesions. Serious consequences of the infection are poor body condition, sterility in bulls and eventual death. The role of host/parasite-dependent factors, which play a major role in the pathogenesis of the disease, is not yet fully elucidated. Isolate/strain virulence, parasite stage, dose and the route of parasite inoculation were studied under different experimental conditions, which make it difficult to compare the results. Data on host-dependent factors obtained from naturally infected cattle showed that (i) the seroprevalence of infection is similar in both sexes; (ii) seropositivity increases with age; (iii) both beef and dairy cattle are susceptible to the infection; and (iv) the cell-mediated immune response is likely to play a major role because a T cell response has been observed around several tissue cysts. Whether colostral antibodies are protective and to what extent the humoral immune response might reflect the disease/protection status require further research. Thus, a well-established experimental bovine model could help to clarify these important questions. The dynamics of B. besnoiti infection in cattle and available knowledge on relevant factors in the pathogenesis of the infection are reviewed in the present work.

A review on bovine besnoitiosis: a disease with economic impact in herd health management, caused by Besnoitia besnoiti (Franco and Borges, )

Bovine besnoitiosis is caused by the largely unexplored apicomplexan parasite Besnoitia besnoiti. In cows, infection during pregnancy often results in abortion, and chronically infected bulls become infertile. Similar to other apicomplexans B. besnoiti has acquired a largely intracellular lifestyle, but its complete life cycle is still unknown, modes of transmission have not been entirely resolved and the definitive host has not been identified. Outbreaks of bovine besnoitiosis in cattle were described in the 1990s in Portugal and Spain, and later several cases were also detected in France. More cases have been reported recently in hitherto unaffected countries, including Italy, Germany, Switzerland, Hungary and Croatia. To date, there is still no effective pharmaceutical compound available for the treatment of besnoitiosis in cattle, and progress in the identification of novel targets for intervention through pharmacological or immunological means is hampered by the lack of molecular data on the genomic and transcriptomic level. In addition, the lack of an appropriate small animal laboratory model, and wide gaps in our knowledge on the host-parasite interplay during the life cycle of this parasite, renders vaccine and drug development a cost- and labour-intensive undertaking.

A century of bovine besnoitiosis: an unknown disease re-emerging in Europe

Bovine besnoitiosis, which is caused by the cyst-forming apicomplexan parasite Besnoitia besnoiti, is a chronic and debilitating vector-borne disease characterized by both cutaneous and systemic manifestations. In Europe, this parasitic disease appeared in a few restricted areas in France and Portugal since the first recorded cases in the beginning of the 20th century. However, at present, the disease is considered to be re-emerging by the European Food Safety Authority due to an increased number of cases and the geographic expansion of besnoitiosis into cattle herds in several European countries. In this review, we will provide an update of the epidemiology and impact of B. besnoiti infection. Strategies to control this parasitic disease will also be discussed.

First serosurvey of Besnoitia spp. infection in wild European ruminants in Spain

Besnoitia besnoiti has been reported to affect cattle, wildebeest, kudu and impala, and B. tarandi other wild ruminants (caribou, reindeer, mule deer and musk ox), causing similar characteristic clinical signs and lesions. However, both Besnoitia species have been reported in different geographical areas and the link between the sylvatic and domestic life cycles of Besnoita spp. in wild ruminants and cattle remains unknown. The aim of this study was to evaluate the presence of specific antibodies against Besnoitia spp. in wild ruminants in Spain. A wide panel of sera from red deer (Cervus elaphus) (n=734), roe deer (Capreolus capreolus) (n=124), chamois (Rupicapra pyrenaica) (n=170) and mouflon (Ovis musimon) (n=20) collected from different locations of Spain was analyzed. Beef cattle were present in all sampled areas and, interestingly, bovine besnoitiosis has been widely reported in some of them (e.g., Pyrenees and Central Spain). Sera samples were first examined with an Enzyme-Linked Immunosorbent Assay (ELISA). For red deer and roe deer, the ELISA was standardized with positive and negative control sera from several Cervidae species (100% Se and 98% Sp). Chamois and mouflon sera samples were tested with a previously reported ELISA validated for bovine sera (97% Se and 95% Sp) using protein G as a conjugate. Positive results by ELISA were confirmed a posteriori with a tachyzoite-based Western blot. Sixty-one sera samples from red deer and 17 sera samples from roe-deer were seropositive or doubtful by ELISA. All samples from mouflon were seronegative and 15 sera samples from chamois were considered doubtful. B. besnoiti exposure was only confirmed clearly by Western blot in one red deer and one roe deer from the Spanish Pyrenees where the disease is traditionally endemic. This is the first serological report of Besnoitia spp. infection carried out in European wild ruminants and the results show that specific antibodies are present at least in red deer and roe-deer. Thus, wild ruminants from endemic regions of bovine besnoitiosis should be further studied because they may be putative reservoirs of the parasite.