Prevalence of Neospora caninum and bovine viral diarrhoea virus in dairy cows in Southern Vietnam

The main purpose of this study was to investigate the prevalence of Neospora caninum and bovine viral diarrhoea virus (BVDV) in some dairy herds in Southern Vietnam, and to ascertain whether there were differences in seroprevalences between herds with imported and locally bred cows. Serum samples collected on five state farms and 97 smallholder herds were analysed for the presence of antibodies to N. caninum and BVDV. All BVDV antibody-negative sera were further tested by antigen-ELISA in order to identify persistently infected individuals. The N. caninum prevalence varied between 16% and 53% in the state herds, and was higher in the four herds that had imported cows than in the herd that only had locally bred cows. Nineteen percent of the samples collected on smallholder farms, which all had only locally bred cows, had antibodies to N. caninum. The BVDV seroprevalence varied between 58% and 93% on the state farms. In smallholder herds, the prevalence of BVDV among the sampled cows was 18% and even lower on the state farms. Despite the high seroprevalence for BVDV in the state herds, no persistently BVDV infected cows were found. Given the high prevalence for Neospora and BVDV among herds with imported cows, it seems advisable to test for both infections before cattle are imported into the country.     

Malaria in cynomolgus monkeys used in toxicity studies in Japan

Plasmodium spp. protozoa cause malaria and are known to infect humans and a variety of animal species including macaque monkeys. Here we report both our experience with malaria recrudescence in cynomolgus monkeys (Macaca fascicularis) in a toxicity study and the results of a survey on Plasmodium infection in cynomolgus monkeys imported to Japan for laboratory use. A cynomolgus monkey from the toxicity study presented with severe anemia and Plasmodium protozoa in erythrocytes on a thin blood smear and was subsequently diagnosed with symptomatic malaria. In this animal, congestion and accumulation of hemozoin (malaria pigment) in macrophages were noted in the enlarged and darkly discolored spleen. As a follow-up for the experience, spleen sections from 800 cynomolgus monkeys in toxicity studies conducted between 2003 and 2013 were retrospectively examined for hemozoin deposition as a marker of Plasmodium infection. The origin of the animals included Cambodia, China, Indonesia, and Vietnam. Hemozoin deposition was confirmed in 44% of all examined monkeys. Monkeys from Indonesia showed the highest incidence of hemozoin deposition (approx. 80%). A high prevalence of Plasmodium infection in laboratory monkeys was also confirmed with polymerase chain reaction (PCR) by using Plasmodium genus-specific primers. Although Japan is not a country with endemic malaria, it is important to be aware of the prevalence and potential impact of background infection with Plasmodium spp. and recrudescence of symptomatic malaria in imported laboratory monkeys on pharmaceutical toxicity studies.     

A seroepidemiological study of bovine pestivirus in Queensland beef and dairy herds conducted in 1994/95

OBJECTIVE: To describe the distribution and prevalence of cattle herds with detectable antibody to bovine pestivirus in Queensland in 1994/95. MATERIALS AND METHODS: The study used 7,838 serum samples collected from 250 herds in Queensland, as part of a structured animal health surveillance program conducted in 1994 and 1995. Samples were collected from female cattle bred on the property. In each herd, 10 to 20 heifers less than two years of age and 10 to 15 older cows were sampled giving a 95% probability of detecting one or more seropositive animals if the seroprevalence was approximately 10% or greater. Sera were analysed for antibodies to bovine pestivirus using a virus neutralisation test. RESULTS: Total cattle numbers in sampled herds varied from 62 to 24,600 head, while total area of properties sampled varied from 50 to 395,400 hectares. Eleven percent of herds contained no seropositive animals among those sampled, and in 38% of herds, all sampled cattle aged one to two years of age were seronegative. There was a trend for larger herds to have one or more animals seropositive for bovine pestivirus (chi-squared for Linear trend = 3.656, p = 0.056). Herds with more than 500 head of cattle were significantly more likely than herds with less than 500 head to contain one or more seropositive animals in any age group (prevalence ratio = 1.12; 95% confidence interval 1.01 - 1.23; p = 0.026). Age specific seroprevalence increased from around 10% in heifers, to between 75% and 85% in cows aged 10 years. The average annual incidence risk for bovine pestivirus infection varied from 0.12 to 0.24 seroconversions per cattle year at risk, and did not vary with age. The overall crude seroprevalence adjusted for herd size was 45%. There was a wide range of seroprevalence recorded for each level of stocking intensity. CONCLUSIONS: This survey provides valuable baseline data on bovine pestivirus infection in Queensland cattle herds.     

A Serosurvey of Crimean‐Congo Haemorrhagic Fever Virus in Dairy Cattle in Iran

A seroepidemiological survey to determine the prevalence of Crimean‐Congo haemorrhagic fever (CCHF) virus among dairy cattle in Iran was carried out during 2006 and 2008. Blood samples were collected from 876 animals in five different provinces of the country. Sera were tested by a sandwich enzyme‐linked immunosorbent assay (ELISA) for quantitative determination of antibodies to CCHF virus. Serological evidence of infection was noted in 52 (5.9%) of 876 dairy cattle. Antibody prevalence increased with age; 78.8% seroprevalence in cattle older than 3 years versus 21.2% in animals less than 2 years old. There was a difference between provinces representing north‐east (11.7%) and east (2%) of Iran.     

Canine distemper virus in coyotes: a serologic survey

Serum samples from 228 coyotes were selected randomly from a serum bank assembled from Texas from 1975 to 1984 and were evaluated serologically for neutralizing antibodies against canine distemper virus (CDV). One hundred and twenty-eight (56%) of the 228 coyotes had antibody titers of greater than or equal to 1:5 against CDV (seropositive). The serologic prevalence (seroprevalence) of antibodies against CDV infection was higher in the spring (62%) than in the fall (40%). The seroprevalence of CDV in various age groups was different; 25 of 101 coyotes (25%) were seropositive at less than 1 year of age, 35 of 52 (67%) were positive between 1 and 2 years of age, and 68 of 75 (91%) were positive at greater than or equal to 2 years of age. The results indicated that CDV was enzootic in coyote populations of southern Texas, with an increasing number of seropositive coyotes noted annually. The sex of the coyote did not appear to be related to the seroprevalence against CDV.     

Prevalence of vesivirus in a laboratory-based set of serum samples obtained from dairy and beef cattle

OBJECTIVE: To examine sera obtained from dairy and beef cattle to detect antibodies against vesivirus and compare seroprevalence among cattle within the sample population. SAMPLE POPULATION: Cattle sera from 8 western states and Maryland submitted to the Washington Animal Disease Diagnostic Laboratory during 1999 and 2000. PROCEDURE: Sera were analyzed for vesivirus-specific antibodies by use of a recombinant vesivirus-San Miguel sea lion virus serotype 5-capsid peptide antigen in an indirect ELISA. RESULTS: Overall, 693 sera were tested and 105 (15.2%) had positive results. Seropositive cattle were from 7 states (all cattle from Montana and Maryland 10 and 4, respectively were seronegative). Overall seroprevalence for antivesivirus antibody in herds ranged between 0% and 80% (median, 14%). Higher antibody prevalence was significantly associated with older age, dairy rather than beef cattle, and reasons for submission. Logistic regression of factors (abortion, respiratory tract disease, and all other reasons for sample submission) revealed that older age and other reasons were independently associated with higher seroprevalence. Higher seropositive optical density values for the ELISA were observed among older cattle and cattle that aborted, compared with values for cattle with respiratory tract disease or other reasons for submission. CONCLUSIONS AND CLINICAL RELEVANCE: This laboratory-based surveillance sample provided a point estimate of seroprevalence against vesivirus among cattle in 9 US states. This suggests that vesivirus infection is widespread with high prevalence in some herds. Risk factors associated with vesivirus seroprevalence in beef and dairy cattle should be confirmed in population-based studies.     

Toxoplasma gondii and Neospora caninum in wildlife: common parasites in Belgian foxes and Cervidae?

Sera from Cervidae were tested for the presence of antibodies against Neospora caninum using ELISA; and against Toxoplasma gondii using SAG1-ELISA and a commercially available agglutination test. The T. gondii seroprevalence was 52% (38/73) in roe deer (Capreolus capreolus), 0% in bred fallow deer (0/4) (Dama dama) and red deer (0/7) (Cervus elaphus). We found 2.7% of the roe deer samples and none of the bred deer samples positive for N. caninum. Brain samples from wild roe deer, red deer and red foxes (Vulpes vulpes) were tested for the presence of T. gondii and N. caninum DNA using multiplex real-time PCR. We detected T. gondii in 18.8% (57/304) of the red foxes and in 1 of the 33 deer samples. N. caninum was found in 6.6% of the red foxes and in 2 roe deer samples. Twenty-six of the T. gondii positive DNA extracts from the red fox samples were genotyped. Twenty-five were type II and only one was found to be type III.     

Molecular characterization of Helicobacter pylori strains isolated from cynomolgus monkeys (M. fascicularis)

We recently reported the occurrence of natural infection with H. pylori in a group of cynomolgus monkeys with chronic active gastritis and gastric erosions. The goal of the present study was to characterize and to compare strains isolated from animals originating from two different geographical areas. Gross and microscopic pathology determined at the time of necropsy was similar in all animals. H. pylori were isolated from specimens harvested in five monkeys (four from Vietnam and one from the Philippines) with gastritis. Isolates from monkeys bred in Vietnam had a similar DNA fingerprint pattern, which was distinct from that of isolates from a monkey bred in the Philippines. All strains were of the s1a vacA subtype, but all the 'Vietnamese' strains were cagA+ and all but one were iceA1 whereas the 'Philippino' strains were cagA- and iceA2. The sequences of the 16S rRNA of the Vietnamese and Philippino strains shared 98% homology and both clustered with H. pylori sequences present in the NCBI database. In conclusion, cynomolgus monkeys can be naturally colonized by H. pylori, and the strains isolated from these animals appear to vary according to the geographical origin, thus indicating probable infection prior to importation. Since some of the cynomolgus monkeys developed antral erosions during natural infection, we propose that this animal model may be used to investigate the role of H. pylori in ulcerogenesis.     

The seroprevalence of Lawsonia intracellularis in horses in The Netherlands

Equine proliferative enteropathy caused by Lawsonia intracellularis is an emerging disease of weanling foals and affects their growth and development. The prevalence of Lawsonia intracellularis in The Netherlands is not known. The aim of the study was to investigate the seroprevalence of Lawsonia intracellularis in horses in The Netherlands. Blood samples were taken from healthy foals before and after weaning and from healthy yearlings and mature horses on farms throughout The Netherlands. These samples were analysed for the presence of Lawsonia intracellularis-specific antibodies with a blocking ELISA. White blood cell count, packed cell volume, and total protein concentration were also measured in all foals. Information regarding housing, pasture access, and contact with pig manure on the premises was obtained for all animals. The prevalence of Lawsonia intracellularis antibodies in foals increased significantly from 15% before weaning to 23% after weaning (p = 0.019); it was 89% in yearlings and 99% in horses older than 2 years. There was no significant difference in seroprevalence between the pasture-kept and stable-confined adult horses (97% and 100%, respectively), and there was no significant influence of contact with pig manure. None of the sampled animals showed clinical disease. In conclusion, the results suggest that Lawsonia intracellularis is widespread in The Netherlands and that seropositivity is not necessarily associated with clinical problems. The high seroprevalence in adult horses suggests long-term persistence of antibodies against Lawsonia intracellularis or constant exposure to the bacterium.     

Seroprevalence of Toxoplasma gondii antibodies in captive mithuns (Bos frontalis) from India

One hundred and four mithuns from India were tested for serum antibodies to Toxoplasma gondii by modified direct agglutination test. The overall prevalence of T. gondii antibodies in mithun was 28% (95% CI=19-37). Highest (prevalence rate=46, 95% CI=30-62) seroprevalence of T. gondii antibodies was found in mithuns above 3 years of age and lowest (prevalence rate=14, 95% CI=1-27) in mithuns of 6 months-1 year old. No statistically significant difference was observed between male (prevalence rate=23, 95% CI=10-36) and female (prevalence rate=31, 95% CI=20-42) seroprevalences (P=0.53). Significant difference was observed in the seroprevalence of T. gondii antibodies in mithuns of different strains with the highest (48%) seroprevalence recorded in Arunachal and lowest (14%) in Mizoram strain. The seroprevalence was higher in farm located at lower altitude (305 m a.s.l.) than the farm located at higher altitude (2134 m a.s.l.). This is the first serologic survey for T. gondii antibodies performed on mithuns from India.     

Neospora caninum and bovine virus diarrhoea virus infections in Swedish dairy cows in relation to abortion

The protozoan parasite Neospora caninum and bovine virus diarrhoea virus (BVDV) are recognized as important causes of bovine abortion and congenital disease worldwide. In this study, serological investigations were performed to estimate the prevalence of N. caninum infection in Swedish dairy cattle, to assess to what extent it may affect abortion rates, and to determine possible effects of coinfection with BVDV. The overall N. caninum seroprevalence in Swedish dairy cows was estimated at 2% (16/780), and the BVDV seroprevalence was 32% (249/780). Among aborting cows from herds with abortion problems, 7% (26/378) had antibodies to N. caninum and 42% (153/378) to BVDV. Seventeen of the N. caninum positive animals also had antibodies to BVDV. There was a statistically significant (P = 0.013) association between presence of antibodies to N. caninum and BVDV. In a case-control study comprising sera from cows in herds without recognized abortion problems, 6% (5/89) and 1% (1/89) of sera from aborting and non-aborting cows, respectively, had antibodies to N. caninum. Two of the N. caninum seropositive aborting cows also had antibodies to BVDV. These results confirm that N. caninum infection is associated with bovine abortion in Sweden and also indicate that there might be concurrent effects of N. caninum and BVDV. It is concluded that Swedish dairy cows have a low prevalence of N. caninum infection which is favourable in relation to possible future control programmes.     

Seroepidemiology of rinderpest in bovids in Sri Lanka using the enzyme linked immunosorbent assay (ELISA) technique

Approximately 0.2% (n=4397) of the bovids (cattle and buffalo) in Sri Lanka were sampled, from June 1992 using a multi-stage sampling procedure. Serum antibodies for the rinderpest virus were detected using the competitive enzyme-linked immunosorbent assay. The age, the agroclimatic zone, the management system practiced in the farms, and the vaccination history of the sampled bovids were studied as potential risk factors for being seropositive.

The prevalence of rinderpest antibodies in non-vaccinated bovids was 3.5% (n=4101). The prevalence was higher in the dry zone (9%; where the outbreak emerged in 1987), compared to bovids in the other zones (1%). Seropositive bovids over three years of age were approximately at fourfold higher chances of being seropositive compared to those that were ≤3 years old. The higher prevalence in older animals is probably due to exposure to the virus during the 1987 epidemic. Bovids from the dry zone (annual rainfall 20 to 35 inches) were at higher odds of being seropositive even after controlling for the possible effects of age, agroclimatic zone, management system and vaccination. The fact that 62% of bovids from the dry zone in this study were reared under extensive management system (free grazing) which allow unrestricted contact between animals, may be the reason for the above finding. A relatively poor response to vaccination observed in vaccinated bovids (seroprevalence=12%; n=296) could be attributed to difficulties in maintaining the vaccine at recommended temperatures in the field. This is the first island-wide study on seroprevalence of rinderpest in Sri Lanka.     

Reduced likelihood of bovine coronavirus and bovine respiratory syncytial virus infection on organic compared to conventional dairy farms

The prevalence of antibodies to bovine coronavirus (BCV) and bovine respiratory syncytial virus (BRSV) infections was studied in 20 conventional and 20 organic dairy herds. The organic farms had produced 'certified' milk for at least 2 years. On two occasions, with a 1-year interval, 699 serum samples from 624 peri-parturient cows were tested by ELISA for antibodies to BCV and BRSV. Accompanying data relating to the sampled animals were collected in order to identify potential factors associated with increased antibody prevalence. The antibody prevalence was high at both sampling times with approximately 85% and 80% of animals positive for antibodies to BCV and to BRSV, respectively. Conventional herds had a significantly higher mean antibody prevalence to BCV and BRSV than the organically managed herds (P<0.01). Animal age was significantly associated with increased antibody prevalence (P<0.001). The findings of this study suggest that organic farm management may be effective in reducing the seroprevalence of these viruses relative to conventional farming methods.     

Serological survey of bovine herpesvirus type 1 infection in China

To understand the nationwide seroprevalence of bovine herpesvirus type 1 (BoHV-1) infection of cows in China, 1344 sera of dairy cows from 29 provinces and 765 sera from 6 herds in Hubei province were collected with stratified random sampling. Another 483 sera from imported cows were included. The serum antibody was tested by BoHV-1 gG ELISA. The results demonstrated that the overall nationwide seroprevalence was 35.8% (481/1344), while the prevalence for individual province ranged from 12.1% to 77.8%. Although each province had positive samples, the prevalence was clustered in areas based on the cow population size. In Hubei Province, the overall seroprevalence was 22.2% (170/765) while the prevalence for individual farms varied greatly from 0.0% to 41.5%. The sera from imported cows had a moderate prevalence of 21.7% (105/483).     

Serosurvey of Aujeszky's disease virus infection in European wild boar in Spain

Serum samples from 693 hunted wild boar (Sus scrofa) were analysed by means of a blocking ELISA technique, and the mean (se) prevalence of antibodies to Aujeszky's disease virus was 44 (4) per cent. All the seropositive wild boar were from south central Spain, except for one from central Spain, close to the main positive area. In this area, where large game species are increasingly managed for hunting, the seroprevalence was affected by the type of management. More intensively managed populations had a higher prevalence than wild boar living in natural situations, and the seroprevalence increased with the age of the animals; the seroprevalence was higher in females in all age groups. The seroprevalence in males more than one year old peaked after the breeding season, whereas females of the same age had a higher and constant seroprevalence throughout the year.     

Prevalence of paratuberculosis (Johne's disease) in the Belgian cattle population

The national bovine paratuberculosis (PTB) seroprevalence (apparent prevalence) in the Belgian cattle population was determined by a serological survey that was conducted from December 1997 to March 1998. In a random sample of herds (N=556, 9.5%), all adult cattle of 24 months of age or older (N=13,317, 0.4%) were tested for the presence of antibodies using a commercially available absorbed ELISA test kit. The PTB median within-herd seroprevalence (proportion of detected animals within the seropositive herds) and the PTB individual-animal seroprevalence (proportion of detected animals) were, respectively, 2.9% (quartiles=1.6-5.6) and 0.87% (95% confidence interval (CI)=0.71-1.03). The PTB herd seroprevalence (proportion of detected herds) was 18% (95% CI=14-21).Assuming a test sensitivity and specificity of 45 and 99% [Sweeney et al., 1995. J. Vet. Diagn. Invest. 7 (4), 488; Sockett et al., 1992. J. Clin. Microbiol. 30 (5), 1134], respectively, the median true within-herd prevalence and the true individual-animal were estimated to be 7 and 2%, respectively. The true herd prevalence of Mycobacterium paratuberculosis infection was first estimated according to currently accepted methodology. This calculation revealed that the specificity of the used test has a dramatic effect on the estimation; assuming a test sensitivity of 45% and a true within-herd prevalence of 7%, the true herd prevalence estimation decreased from 36 to 0.8% if the test specificity decreased from 99. 9 to 99%, respectively. This sensitivity analysis showed that the practical limits of the accuracy of the used screening test jeopardize the estimation of the true herd prevalence within reasonable confidence limits, because the within-herd PTB true prevalence was low.For this reason we augmented the herd specificity for herds with larger adult herd size (>5). This was done by increasing the cut-off number of positive cattle required (>/=2) to classify a herd truly positive and including herds with one positive test result if there was historical evidence of PTB (previous diagnosis and/or clinical signs). This approach resulted in an estimated true herd prevalence of M. paratuberculosis infection of 6%. The true herd prevalence for dairy, mixed and beef herds was, respectively, 10, 11 and 3%.     

Seroprevalence of Toxoplasma gondii antibodies in free-ranging mithuns (Bos frontalis) from India

Studies conducted on free-ranging mithuns of Nagaland, India revealed that the overall seroprevalence of antibodies to Toxoplasma gondii in mithun was 42% (95% CI = 33-51) when detected by modified direct agglutination test. Highest (prevalence = 57%, 95% CI = 43-71) seroprevalence was found in mithuns above 3 years of age and the lowest (prevalence = 18%, 95% CI =4-32) in mithuns of 1-2 years old. No statistically significant difference was observed between male (prevalence = 40%, 95% CI = 26-54) and female (prevalence = 44%, 95% CI = 31-57) seroprevalences. The study also revealed that the maximum number (57%) of animals with the highest titre (1 : 3200) were above 3 years of age. This is the first serological survey for Toxoplasma gondii antibodies in free-ranging mithuns from India.     

Serological Confirmation of Borrelia burgdorferi Infection in Dogs in the Czech Republic

From the epidemiological point of view, dogs are very important since they are considered a suitable indicator of the spread of human borreliosis. Serum samples obtained from healthy, asymptomatic military dogs from 12 different areas in the Czech Republic were examined for IgG antibodies to Borrelia burgdorferi sensu lato (s.l.). The total of 399 serum samples were tested by a whole-cell ELISA. Specific antibodies to Borrelia burgdorferi s.l. were detected in 26 cases (6.5%). In different localities, the seroprevalence varied from 0.0% to 28.6%. Two local isolated strains Br-75 (Borrelia afzelii) and Br-97 (Borrelia garinii) were used as antigens. A total of 22 (5.5%) were positive for antibodies to Borrelia afzelii and 19 (4.8%) were positive for antibodies to Borrelia garinii. Fifteen cases were positive for both antibodies. A significantly higher seroprevalence was found in younger dogs (1–3 years) than in older ones (p < 0.05). An analysis of seroprevalence by months of sampling showed no significant difference (p > 0.05).     

Prevalence and incidence of Newcastle disease and prevalence of Avian Influenza infection of scavenging village chickens in Timor-Lesté

A longitudinal study to monitor prevalence and incidence of antibodies against Newcastle disease (ND) virus and prevalence of antibodies against Avian Influenza (AI) virus in scavenging village chickens was conducted in 20 villages within 4 districts of Timor-Lesté. A total of 3600 blood samples was collected from 1674 individual birds in 300 household chicken flocks during three sampling periods (December 2008-February 2009, March-May 2009, and June-August 2009). The mean interval between household visits was 101.6±1.9 days. None of the birds enrolled in the study was vaccinated against ND or AI. A haemagglutination inhibition (HI) test was used to determine antibody titres against ND virus and a competitive ELISA and HI tests were used to detect antibody against AI virus. The bird-level ND seroprevalence pooled across all samplings (adjusted for clustering by households) was 4.4% (95% CI 3.5-5.2). The bird-level ND seroprevalence in each of the three sampling periods (adjusted for clustering by household) was 3.0% (95% CI 2.0-4.0), 6.6% (95% CI 5.1-8.0) and 3.6 (95% CI 2.5-4.6), respectively. A total of 12.6% individual birds tested ND seropositive at least once over the total study period (95% CI 10.5-14.7). The flock-level ND seroprevalence (at least one bird tested had antibodies against ND virus) pooled across all samplings was 15.9% (95% CI 13.5-18.3). A total of 35.3% flocks had a minimum of one bird being ND seropositive at least once over the study period. The bird-level incidence rate for the period between the first and the second sampling and between the second and the third sampling was 5.6 (95% CI 4.1-7.5) and 0.5 (95% CI 0.5-3.8) per 10,000 bird-years-at-risk, respectively. A total of 1134 serum samples from the last sampling period between June and August 2009 was tested for antibodies against AI virus. Only 4 samples tested Influenza A positive, indicating a bird-level seroprevalence level for Influenza A of 0.4% (CI 0.0-0.7%). These Influenza A positive samples were further tested for HI antibodies against AI virus subtypes of H5N1, H5N3, H7N3 and H9N2, but all tested negative, suggesting that the influenza antibodies in those four birds resulted from exposure to low pathogenic AI viruses of different H subtypes. Our results indicate that village chickens in Timor-Lesté are exposed to ND virus; there was a higher risk of infection during the early months of 2009 than either immediately prior or subsequent to this. No evidence of infection of village chickens with H5, H7 or H9 AI viruses was detected in this study.     

Prevalence of bovine parvovirus infection in Ontario dairy cattle.

Studies were conducted to determine prevalence and dynamics of bovine parvovirus (BPV) infection. Dairy cows from 29 randomly selected herds in southwestern Ontario were tested twice, one year apart, for the presence of hemagglutination inhibition (HI) antibodies against BPV. Fifty-one percent of 1141 cows tested had BPV-HI titers > 1:32. One year later, the seroprevalence was 83% in 1131 cows from the same farms. The herd mean seroprevalence was 49% and 86% for the year-1 and year-2 samples, respectively. Evidence of BPV infection was found in 96% (27/28) of herds in year-1 and 100% of herds in year-2. A comparison of titers from 716 cows tested twice showed evidence of frequent BPV infection. Sixty-two percent of 326 animals selected in a systematic manner from 40 Guelph area dairy farms had BPV-HI titers > 1:32. The herd mean seroprevalence was 64% Two herds had no animals with titers above the critical titer (1:32) while in one-quarter of the herds all animals exceeded the critical titer.