A herd-level analysis of risk factors for antibodies to Sarcocystis neurona in Michigan equids

Equine protozoal myeloencephalitis (EPM) is a neurological disease of horses and ponies caused by infection of the central nervous system with the protozoan parasite Sarcocystis neurona. A herd-level analysis of a cross-sectional study of serum antibodies to S. neurona in Michigan equids was conducted, using data collected in 1997 for study that included 1121 equids from 98 Michigan horse farms. Our objective was to identify specific herd-level risk factors associated with seropositivity. We tested associations between herd seroprevalence and various farm-management practices (including feed-storage methods and wildlife control). Multivariable models were developed for three strata based on relative opossum abundance (opossum districts). Herd seroprevalence ranged from 0 to 100% (median=57%). No risk factor was significantly associated with herd seroprevalence at P< or = 0.05 in all opossum districts. Our results suggest that equids living in areas with large opossum populations might be infected with S. neurona from multiple sources.     

Seroprevalence of antibotulinum neurotoxin type C antibodies in horses in Israel

REASONS FOR PERFORMING STUDY: Clostridium botulinum type C is prevalent in Israel and outbreaks recorded in many species, other than horses. Association between levels of anti-BoNT/C antibodies and equine grass sickness (EGS) have been demonstrated but seroprevalence of anti-BoNT/C antibodies in horses has not been reported nor has EGS been reported in Israel. OBJECTIVES: To determine the seroprevalence of specific anti-BoNT/C antibodies in horses in Israel and to determine whether age, breed and gender, or geographical region of farms are potential risk factors for exposure to BoNT/C. HYPOTHESIS: Anti-BoNT/C antibodies are prevalent among horses in Israel and farm and horse-level variables are associated with increased risk for exposure. METHODS: Serum samples from 198 horses were collected and the levels of specific anti-BoNT/C antibodies were determined using enzyme-linked immunosorbent assay (ELISA). For each categorical variable indicator variables were created and the odds ratio (OR) and 95% confidence intervals (95% CI) for the outcome variable were calculated using a univariable and multivariable logistic regression models. RESULTS: A total of 61 (30.8%) horses were ELISA positive for anti-BoNT/C IgG antibodies. The farm and its geographical region were associated significantly with seropositivity, horse-level variables, such as gender and breed, were also associated with seropositivity. Quarter Horse and Warmblood mares placed in the southern region of Israel had the highest odds to be tested positive for anti-BoNT/C IgG antibodies. CONCLUSIONS AND POTENTIAL RELEVANCE: Several farm and various horse-level risk factors for exposure to BoNT/C, found in this study, could be correlated to previously reported risk factors of EGS. Studies are required to determine the predisposing factors that cause EGS, which is apparently not present in Israel.     

Seroprevalence of Neospora,Toxoplasma gondii and Sarcocystis neurona antibodies in horses from Jeju island,South Korea

Parasite-specific antibody responses to Neospora spp. and Toxoplasma gondii, antigens were detected using the indirect fluorescent antibody test (IFAT) and immunoblot analysis in a korean equine population located on Jeju island, South Korea (126 degrees 12' E and 33 degrees 34' N). For comparison, a naturally infected Neospora hughesi horse and an experimentally inoculated T. gondii equid (pony) were used. In addition, all samples were tested for antibodies to Sarcocystis neurona by immunoblot analysis. A total of 191 serum samples from clinically normal horses were evaluated. Only 2% (4 out of 191) and 2.6% (5 out of 191) of the samples had showed reactivity at 1:100 using the IFAT for Neospora spp. and T. gondii, respectively. For T. gondii, two samples matched the antigen banding pattern of the positive control by immunoblot analysis. No sample was positive for N. hughesi by immunoblot analysis in this study. Overall, there was a 1% seroprevalence for T. gondii antibodies in the horses tested based on immunoblot analysis. The seroprevalence for S. neurona and N. hughesi antibodies was 0%. We concluded that these horses are either not routinely exposed to these parasites or antibody titers are not sufficiently elevated to be detectable. It is most likely the former explanation since Jeju island equine farms are isolated from the main land, and the horses were all less than 3 years of age. This na?ve population of horses could be useful when evaluating S. neurona serodiagnostic tests or evaluating potential S. neurona vaccines since exposure risks to S. neurona and closely related parasites are negligible.     

Prevalence of Neospora hughesi and Sarcocystis neurona antibodies in horses from various geographical locations

Parasite-specific antibody responses to Neospora antigens were detected using the immunofluorescent antibody test (IFAT) and immunoblot analysis in select equine populations. For comparison, a naturally infected Neospora hughesi horse and an experimentally inoculated Neospora caninum horse were used. In addition, all samples were tested for antibodies to Sarcocystis neurona by immunoblot analysis. A total of 208 samples was evaluated. The equine populations were derived from five distinct geographic regions. Locations were selected based on distribution of Didelphis virginiana, the native North American opossum which serves as the definitive host for S. neurona. Only 11% of the samples that had positive titers of 1:100 using the IFAT were also positive for antibodies by immunoblot analysis in this study. Overall, there was a 2% seroprevalence for Neospora antibodies in all horses tested based on immunoblot analysis described. The seroprevalence for S. neurona antibodies varied from 0% (New Zealand and Montana) to 54% (Missouri). We concluded that, in testing for antibodies against Neospora antigens using either IFAT or immunoblot analysis, as described, positive results should not be attributed to the presence of antibodies to S. neurona.     

Prevalence of Sarcocystis neurona and Neospora spp. infection in horses from Brazil based on presence of serum antibodies to parasite surface antigen

Sera from 961 horses from Brazil were tested for antibodies against the major surface antigens SnSAG4 and NhSAG1 to determine the seroprevalence of Sarcocystis neurona and Neospora hughesi, respectively. Antibodies against SnSAG4 were detected in 669 (69.6%) of the horses, while antibodies against NhSAG1 were detected in only 24 (2.5%) of the horses. These serologic results suggest that there is a high concentration of S. neurona in the environment of Brazil, which results in marked exposure of horses to this parasite. Additionally, the data further confirm that infection with Neospora spp. is relatively uncommon in horses.     

Seroprevalence of antibodies to Sarcocystis neurona in equids residing in Oklahoma.

A sampling of equids from the state of Oklahoma produced an estimate of seroprevalence of antibody to Sarcocystis neurona to be about 89.2%. This figure represents the highest currently reported regional seroprevalence of antibody to this organism. Regional differences in seroprevalence were found in the western quadrants of the state relative to the eastern quadrants of the state, with a significantly higher seroprevalence in the eastern regions. Thoroughbreds were found to exhibit a statistically significant lower seroprevalence as a breed group when compared with other breeds sampled.     

Epidemiology of Sarcocystis neurona infections in domestic cats (Felis domesticus) and its association with equine protozoal myeloencephalitis (EPM) case farms and feral cats from a mobile spay and neuter clinic

Equine protozoal myeloencephalitis (EPM) is a serious neurologic disease in the horse most commonly caused by Sarcocystis neurona. The domestic cat (Felis domesticus) is an intermediate host for S. neurona. In the present study, nine farms, known to have prior clinically diagnosed cases of EPM and a resident cat population were identified and sampled accordingly. In addition to the farm cats sampled, samples were also collected from a mobile spay and neuter clinic. Overall, serum samples were collected in 2001 from 310 cats, with samples including barn, feral and inside/outside cats. Of these 310 samples, 35 were from nine horse farms. Horse serum samples were also collected and traps were set for opossums at each of the farms. The S. neurona direct agglutination test (SAT) was used for both the horse and cat serum samples (1:25 dilution). Fourteen of 35 (40%) cats sampled from horse farms had circulating S. neurona agglutinating antibodies. Twenty-seven of the 275 (10%) cats from the spay/neuter clinic also had detectable S. neurona antibodies. Overall, 115 of 123 (93%) horses tested positive for anti-S. neurona antibodies, with each farm having greater than a 75% exposure rate among sampled horses. Twenty-one opossums were trapped on seven of the nine farms. Eleven opossums had Sarcocystis sp. sporocysts, six of them were identified as S. neurona sporocysts based on bioassays in gamma-interferon gene knockout mice with each opossum representing a different farm. Demonstration of S. neurona agglutinating antibodies in domestic and feral cats corroborates previous research demonstrating feral cats to be naturally infected, and also suggests that cats can be frequently infected with S. neurona and serve as one of several natural intermediate hosts for S. neurona.     

Seroprevalence of Toxoplasma gondii, Sarcocystis neurona, and Encephalitozoon cuniculi in three species of lemurs from St. Catherines Island, GA, USA

In the current study, we determined the seroprevalence of Toxoplasma gondii, Sarcocystis neurona, and Encephalitozoon cuniculi in three species of lemurs from St. Catherines Island, Georgia. Serum samples were tested from 52 ring-tailed lemurs (Lemur catta), six blue-eyed black lemurs (Eulemur macaco flavifrons), and four black and white ruffed lemurs (Varecia variegata variegata) using an agglutination assay. Three ring-tailed lemurs (5.8%) were positive for T. gondii (titer of 1:50); one ring-tailed lemur (1.9%) and one black and white ruffed lemur (25%) were positive for S. neurona (titers of 1:1000); and one ring-tailed lemur (1.9%) was positive for E. cuniculi (titer of 1:400). All blue-eyed black lemurs were negative for antibodies to T. gondii, S. neurona, and E. cuniculi. This is the first detection of antibodies to T. gondii in ring-tailed lemurs and antibodies to S. neurona and E. cuniculi in any species of prosimian.     

A systematic review and meta‐analysis of predictors of human hepatitis E virus exposure in non‐endemic countries

The reported incidence of clinical hepatitis E cases is rising in some non‐endemic countries, with concurrent concerns regarding potential hepatitis E virus (HEV) contamination of the blood supply. Therefore, the characterization of major potential sources of human HEV exposure is important to inform risk assessment and public health policy. A systematic review was conducted, including a comprehensive search in six electronic bibliographic databases, verified by hand‐searching reference lists of HEV reviews, and a grey literature search, of the broad research question ‘what is the evidence of the association between predictors of human HEV exposure, and HEV IgG seropositivity, in non‐endemic countries?’ Using forms designed a priori, captured studies were appraised at first‐level screening, second‐level characterization, and third‐level data extraction and risk of bias assessment. Meta‐analysis yielded summary estimates of association between potential predictors and odds of HEV seropositivity. Meta‐analysis and meta‐regression of the odds of HEV seroprevalence in specific groups characterized potential sources of HEV exposure. From 4,163 captured citations, 245 relevant studies underwent data extraction, investigating HEV seroprevalence or predictors in both healthy subjects and targeted patient groups. Across these groups, increasing age was a predictor of HEV IgG seropositivity. Both human immunodeficiency virus patients and haemodialysis patients had significantly increased odds of HEV seropositivity relative to the general population. Working with pigs, in forestry, or in hospitals, was significantly associated with increased odds of HEV seropositivity, as were consumption of meat, pork or game meat, or hunting. Chronological time was not associated with HEV seropositivity within our data sets. Further study of the distribution of potential dietary or behavioural predictors between high and lower prevalence areas within non‐endemic countries could improve our understanding of the relative importance of specific HEV transmission pathways.     

Comparison of Sarcocystis neurona isolates derived from horse neural tissue

Sarcocystis neurona is a protozoan parasite that can cause neurological deficits in infected horses. The route of transmission is by fecal-oral transfer of sporocysts from opossums. However, the species identity and the lifecycle are not completely known. In this study, Sarcocystis merozoites from eight isolates obtained from Michigan horses were compared to S. neurona from a California horse (UCD1), Sarcocystis from a grackle (Cornell), and five Sarcocystis isolates from feral opossums from Michigan.Comparisons were made using several techniques. SDS-PAGE analysis with silver staining showed that Sarcocystis spp. from the eight horses appeared the same, but different from the grackle isolate. One Michigan horse isolate (MIH6) had two bands at 72 and 25kDa that were more prominent than the UCD1 isolate and other Michigan horse isolates. Western blot analysis showed that merozoites of eight of eight equine-derived isolates, and the UCD1 S. neurona isolate had similar bands when developed with serum or CSF of an infected horse. Major bands were seen at 60, 44, 30, and 16kDa. In the grackle (Cornell) isolate, bands were seen at 60, 44, 29, and 16kDa. DNA from merozoites of each of the eight equine-derived isolates and the grackle-derived isolate produced a 334bp PCR product (Tanhauser et al., 1999). Restriction fragment length polymorphism (RFLP) analysis of these horse isolates showed banding patterns characteristic for S. neurona. The grackle (Cornell) isolate had an RFLP banding pattern characteristic of other S. falcatula species. Finally, electron microscopy examining multiple merozoites of each of these eight horse isolates showed similar morphology, which differed from the grackle (Cornell) isolate. We conclude that the eight Michigan horse isolates are S. neurona species and the grackle isolate is an S. falcatula species.     

Seroprevalence of and risk factors for infectious bovine rhinotracheitis in beef cattle herds of Yucatan,Mexico

The main objective of this cross-sectional study was to estimate the seroprevalence of infectious bovine rhinotracheitis (IBR) in a population of non-vaccinated beef cattle in the livestock region of Yucatan, Mexico and to determine potential risk factors related to the seroprevalence. Also, we estimated the intraherd correlation (r_e) and design effect (D) of IBR seropositivity. Cattle were selected by two-stage cluster sampling. Blood samples were collected from 564 animals from 35 herds. Sera were tested for antibodies against IBR using the serum-neutralisation test. Information regarding the herd and each animal sampled were recorded through a personal interview with the farmer or farm manager. The data were analysed using fixed-effects logistic multiple regression. Thirty-four of the 35 herds had at least one seropositive animal. The animal true seroprevalence was 54.4%. Animals in large herds or in production had higher odds of seropositivity than those in small herds or growing. The r_e and D were 0.17 and 3.62, respectively.     

Risk of postnatal exposure to Sarcocystis neurona and Neospora hughesi in horses

OBJECTIVE: To estimate risk of exposure and age at first exposure to Sarcocystis neurona and Neospora hughesi and time to maternal antibody decay in foals. ANIMALS: 484 Thoroughbred and Warmblood foals from 4 farms in California. PROCEDURE: Serum was collected before and after colostrum ingestion and at 3-month intervals thereafter. Samples were tested by use of the indirect fluorescent antibody test; cutoff titers were > or = 40 and > or = 160 for S neurona and N hughesi, respectively. RESULTS: Risk of exposure to S neurona and N hughesi during the study were 8.2% and 3.1%, respectively. Annual rate of exposure was 3.1% for S neurona and 1.7% for N hughesi. There was a significant difference in the risk of exposure to S neurona among farms but not in the risk of exposure to N hughesi. Median age at first exposure was 1.2 years for S neurona and 0.8 years for N hughesi. Highest prevalence of antibodies against S neurona and N hughesi was 6% and 2.1 %, respectively, at a mean age of 1.7 and 1.4 years, respectively. Median time to maternal antibody decay was 96 days for S neurona and 91 days for N hughesi. There were no clinical cases of equine protozoal myeloenchaphlitis (EPM). CONCLUSIONS AND CLINICAL RELEVANCE: Exposure to S neurona and N hughesi was low in foals between birth and 2.5 years of age. Maternally acquired antibodies may cause false-positive results for 3 or 4 months after birth, and EPM was a rare clinical disease in horses < or = 2.5 years of age.     

Assessing the agreement of Western blot test results for paired serum and cerebrospinal fluid samples from horses tested for antibodies to Sarcocystis neuronaf

Equine protozoal myeloencephalitis (EPM) is a neurological disease of equids that is caused by infection of the central nervous system with Sarcocystis neurona. Veterinarians diagnose EPM by performing a neurological examination and by ordering Western blot tests for antibodies to S. neurona in the blood and/or cerebrospinal fluid (CSF). The negative predictive value of the Western blot test is generally accepted to be high for both serum and CSF. If the agreement between serum and CSF test results is strong, serum tests could be used to substitute for CSF tests in some cases. The purpose of this study was to assess the agreement of the results of 181 paired serum and CSF Western blot antibody tests on equine samples submitted to the Michigan State University Animal Health Diagnostic Laboratory. The agreement of the paired serum and CSF results was assessed for three possible test outcomes--negative, positive or suspect. An additional analysis was performed in which samples reported as suspect were reclassified as negative. The kappa statistic for negative, positive and suspect samples was 0.469. The kappa statistic for the analysis in which the suspect results were reclassified as negative was 0.474. In addition, 29% (33/112) CSF samples from seropositive horses were negative. Our results demonstrate that the level of agreement is only moderate in diagnostic samples. This supports the practice of testing CSF of seropositive horses suspected of having EPM.     

Toxoplasma gondii infection in Polish farmed mink

The aim of this study was to determine the seroprevalence of Toxoplasma gondii antibodies in Polish farmed mink according to way of feeding as well as to confirm the role of toxoplasmosis in reproductive losses in mink farms. The serological examinations were carried out on 961 mink randomly selected from 12 Polish farms. Blood sera were examined for the presence of T. gondii antibodies with the use of the latex agglutination test. The examinations for the presence of T. gondii in organ tissues were performed on five neonatal mink kits with the use of immunofluorescence method. In total 133 (13.9%) out of 961 examined mink had T. gondii antibodies. In large farms the seropositivity was lower (2.9%), than in small farms (26.33%) (P < 0.001). Significant difference was found in seroprevalence according to way of feeding. In farms feeding fish, percentage of seropositivity was lower (2.2%), than in farms based on non-frozen slaughter offal (43.4%). Titres of T. gondii antibodies were usually lower than 120 IU/ml. Using the immunofluorescence method, T. gondii was detected in impression smears from liver and brain of two neonatal mink kits derived from one seropositive female.     

Prevalence of Sarcocystis neurona sporocysts in opossums (Didelphis virginiana) from rural Mississippi

Sarcocystis species sporocysts were found in intestinal scrapings from 24 of 72 opossums (Didelphis virginiana) from rural Mississippi. The number of sporocysts in each opossum varied from a few ( < 100000) to 187 million. Sporocysts from 24 opossums were bioassayed for Sarcocystis neurona infections by feeding to gamma-interferon knockout (KO) mice. S. neurona was detected in the brains of KO mice fed sporocysts from 19 opossums by immunohistochemical staining with anti-S. neurona specific polyclonal rabbit serum, and by in vitro culture from the brains of KO mice fed sporocysts. The isolates of S. neurona from opossums were designated SN16-OP to SN34-OP. Merozoites from 17 of 19 isolates tested at the 25/396 locus were identical to previously described S. neurona isolates from horses. The high prevalence of S. neurona sparocysts in D. virginiana suggests that this opossum constitutes an ample reservoir of infection in the southern United States.     

Interpretation of the detection of Sarcocystis neurona antibodies in the serum of young horses

Horses that are exposed to Sarcocystis neurona, a causative agent of equine protozoal myeloencephalitis, produce antibodies that are detectable in serum by western blot (WB). A positive test is indicative of exposure to the organism. Positive tests in young horses can be complicated by the presence of maternal antibodies. Passive transfer of maternal antibodies to S. neurona from seropositive mares to their foals was evaluated. Foals were sampled at birth (presuckle), at 24h of age (postsuckle), and at monthly intervals. All foals sampled before suckling were seronegative. Thirty-three foals from 33 seropositive mares became seropositive with colostrum ingestion at 24h of age, confirming that passive transfer of S. neurona maternal antibodies occurs. Thirty-one of the 33 foals became seronegative by 9 months of age, with a mean seronegative conversion time of 4.2 months. These results indicate that evaluation of exposure to S. neurona by WB analysis of serum may be misleading in young horses.     

Seroprevalence of and risk factors for brucellosis of goats in herds of Michoacan, Mexico

Our objectives were to estimate the seroprevalence of Brucella melitensis, and to identify some risk factors associated with goat seropositivity in Michoacan, Mexico. Blood samples were collected from 5114 animals from 79 herds. Sera were tested for antibodies against B. melitensis using the Rose Bengal plate test and the complement-fixation test. Information regarding the herds and each animal sampled were recorded through a personal interview at the farm. We used random-effects multivariable logistic regression to analyze our data. Fifty-six herds of the 79 tested had at least one seropositive animal. The animal-level true seroprevalence was 9.8% (CI = 8.8, 10.7). Animals in large herds (>34 animals), in herds with high stock density (>3.5 animals/m²) or animals >24 months old had higher odds of seropositivity (2.0, 1.7 and 1.8, respectively) than those in small herds, in herds with low stock density or animals ≤24 months old.     

Familial and herd-level associations with paratuberculosis enzyme-linked immunosorbent assay status in beef cattle

A cross-sectional study was performed to determine the odds of having a positive paratuberculosis ELISA result if the dam was ELISA positive in Texas beef cattle, adjusted for individual and herd-level risk factors for seropositivity. Texas beef cattle (n = 2,621) were tested for paratuberculosis by using a commercial ELISA and microbiologic culture of feces for Mycobacterium avium subsp. paratuberculosis (MAP). Pedigree data were collected to identify dam-and sire-offspring pairs. Bayesian mixed-effects logistic regression was used to estimate the odds of seropositivity associated with age, dam ELISA status, sire ELISA status, herd size, herd history of clinical paratuberculosis, within-herd seroprevalence, within-herd fecal MAP prevalence, and within-herd fecal non-MAP Mycobacterium spp. prevalence. Herd of residence was included as a random effect to account for the correlation of observations within the same herd. Statistically probable associations were observed between ELISA status and herd fecal MAP prevalence [OR (odds ratio) 1.28 per 1% increase; P < 0.001] and herd seroprevalence (OR 1.21 per 1% increase; P < 0.001). The association with dam ELISA status was small (OR 1.35) and not highly probable (P = 0.69). Results indicate that use of dam ELISA status to make culling decisions in beef cattle may not improve the success of paratuberculosis control programs. Alternative strategies may be more effective for reducing the odds of seropositivity.     

Seroprevalence,spatial distribution and risk factors of Borrelia burgdorferi sensu lato in Jordan

Lyme borreliosis has not been studied in Jordan or in much of the Middle East. However, limited research indicates that the tick vector, Ixodes ricinus, exists in the region. This study examined the seroprevalence of B. burgdorferi s.l. in Jordan and potential demographic and zoonotic risk factors for seropositivity. Serum samples of 824 apparently healthy participants from 11 governorates in Jordan were tested for B. burgdorferi s.l. using Enzygnost Lyme link VlsE/IgG enzyme-linked immunosorbent assay. A validated questionnaire was used to collect demographic and animal exposure data. Univariate and multivariate logistic regression were used to identify factors associated with seropositivity. The results showed that 11.7 % (95 % CI, 9.3–14.0 %) of the participants were seropositive for B. burgdorferi s.l.. There was a bimodal age distribution of seroprevalence with higher seroprevalence among individuals <20 and>60 years old. After controlling for governorate of residence, females had 2.77 (95 % CI 1.53–5.00) times greater odds of seropositivity compared to males. Individuals living in the southeastern part of Jordan (Ma’an) had 2.32 (95 % CI, 1.02−5.31) greater odds of seropositivity compared to those living in Amman, the Capital of Jordan, while those living in the northeast had significantly lower odds of seropositivity. This study presents the first evidence of B. burgdorferi s.l. seropositivity in Jordan and suggests several risk factors which were reported in studies conducted elsewhere. This study suggests that Lyme borreliosis should be considered in the differential diagnosis for patients presenting with skin lesions in Jordan.