Arvo Viltrop

Eimeria and Cryptosporidium in Estonian dairy farms in regard to age, species, and diarrhoea

Eimeria and Cryptosporidium are among the most common bovine parasites in the world, but little is known about them in Estonia. Basic field research is needed to gain insight into pathogen dynamics, providing knowledge for veterinarians and research. A survey of 45 Estonian dairy farms in 15 counties was carried out between 2006 and 2007. Three age groups: <3, 3-12, and >12 months old animals were sampled. Collected faeces were examined by quantitative flotation and Ziehl-Neelsen contrast staining, and species examined morphologically. Selected samples containing Cryptosporidium were additionally examined by polymerase-chain-reaction (PCR) and sequencing to determine genotypes. Twelve species of Eimeria were identified, seven previously unknown in Estonia. Main species in samples were E. bovis (30%), E. zuernii (23%), and E. ellipsoidalis (14%). All herds were infected and animals aged 3-12 months were more commonly infected with Eimeria oocysts (63%) than any other group. Calves <3 months shed most oocyst, but high counts were rare. A negative association (slope=-0.16, p<0.001) was found between the number of animals infected with Eimeria and the age category. Cryptosporidium were detected in 84% of the farms, and C. andersoni and C. parvum were successfully identified. Though prevalences of Cryptosporidium in the age groups were similar to the sample prevalence (30%) an increase in the infections was found with increasing age (p<0.001). Higher diarrhoea scores were negatively associated with Eimeria spp. infection (slope=-0.08, p<0.05), whereas Cryptosporidium could not be associated with the presence of diarrhoea. Frequent low intensity infections of animals in all age groups with both parasites apply a constant stress on the animals with impact on health and production. The Estonian results are different compared to available studies in regard of: older animals commonly being infected, finding of modest oocyst counts, and distribution of Eimeria species.

Seroepidemiology of bovine herpesvirus 1 (BHV1) infection among Estonian dairy herds and risk factors for the spread within herds

The objectives of this study were to reassess the herd level and within-herd prevalence of bovine herpesvirus 1 (BHV1) infection in Estonian dairy cattle, estimate the sensitivity and specificity of the enzyme-linked immunosorbent assay (ELISA) for bulk tank milk (BTM) testing and determine the risk factors related to high prevalence of the infection in herds. To estimate the herd prevalence, BTM samples from each of the 1,205 herds that sell milk to dairy companies were analysed for BHV1 antibodies. One hundred and three herds with known BHV1 infection status were selected to estimate within-herd prevalence and to calculate the sensitivity and specificity of BTM ELISA. In these herds serum samples were collected from cows and youngstock, together with BTM samples. A commercial blocking ELISA test was used to analyse samples for antibodies against BHV1. A questionnaire was completed to collect herd data. The sensitivity and specificity of the BTM ELISA were 76.5% and 97.2%, respectively, and the true herd prevalence of BHV1 was calculated to be 22.0%. The herd prevalence increased significantly with herd size, being 3.4% in the smallest category (less than 20 cows) and 85.7% in herds of size over 400. The mean within-herd prevalence was 37.8% (range 1-100, median 31.5). The mean within-herd prevalence increased with herd size. Data from 59 infected herds was used to determine the risk factors associated with high within-herd prevalence (>50%) of BHV1, using logistic regression analysis. As, in some infected herds, the youngstock were uninfected, risk factors for the presence of BHV1 among youngstock from 6 months until calving were analysed. The results indicate the importance of iatrogenic spread of the virus, since the overall within-herd prevalence was higher in those herds in which a veterinarian was an employee of the farm and an inseminator worked only for the particular farm. The presence of bovine viral diarrhoea virus (BVDV) in a herd was associated with a higher prevalence of BHV1.

Association of herd BRSV and BHV-1 seroprevalence with respiratory disease and reproductive performance in adult dairy cattle

BackgroundThe aim of this study was to detect the associations between bovine herpesvirus 1 (BHV-1) status of a herd and respiratory disease (BRD) occurrence and reproductive performance in pregnant heifers and cows. The association between management-related factors and higher BRD occurrence was also estimated.MethodsSerum samples, collected from cows and youngstock from 103 dairy cattle herds, were analyzed for antibodies against BHV-1, bovine respiratory syncytial virus (BRSV), bovine viral diarrhoea virus (BVDV), and Mycoplasma bovis. A questionnaire was used to collect data concerning herd management factors and reproductive performance, as well as the occurrence of clinical signs of respiratory disease in the last two years, as evaluated by the veterinarian or farm manager. Multiple correspondence analysis (MCA) and logistic regression analysis were performed to identify and quantify the risk factors.ResultsA low to moderate prevalence (1-49%) of BRSV antibodies among youngstock was associated with a high occurrence of respiratory disease (OR = 6.2, p = 0.010) in cows and in-calf heifers. Employees of the farm may participate in the spread of such disease. Larger herd size, loose-housing of cows, housing youngstock separately from cows until pregnancy, and purchasing new animals were factors possibly related to a high occurrence of respiratory disease symptoms in pregnant heifers and cows. The highest risk of abortions (> 1.3%) and increased insemination index (number of inseminations per pregnancy) (> 1.9) occurred in herds with a moderate prevalence of BHV-1 antibodies (1-49%) in cows.ConclusionsBHV-1 was not associated with acute respiratory disease in adult dairy cattle, however was significantly related to reproductive performance. BRSV possesses the main role in respiratory disease complex in adult dairy cattle.

Occurrence of clinical mastitis in primiparous Estonian dairy cows in different housing conditions

BackgroundObjectives of the study were to document the impact of some management factors on the occurrence of clinical mastitis in primiparous dairy cows and to identify common udder pathogens of clinical mastitis in freshly calved heifers and multiparous cows on the day of calving.MethodsA one-year study was conducted during 2004 and 2005 in 11 selected Estonian dairy herds. Data consisted of 68 heifers with clinical mastitis and 995 heifers without clinical mastitis on the day of calving. Multivariable logistic regression with a random herd effect was used to investigate any association between housing system or the time interval from movement of heifers to the calving facility and day of calving on occurrence of clinical mastitis. Milk samples for bacteriological analysis were collected from affected heifers and multiparous cows on the day of calvingResultsClinical mastitis occurrence in the study population of freshly calved heifers equalled 6.1 %. Housing system was not a significant risk factor for clinical mastitis of freshly calved heifers.Moving heifers to the cowbarn less than two weeks before calving in tiestall farms increased risk (OR = 5.9 p = 0.001) for clinical mastitis at parturition. The most frequently isolated udder pathogens among heifers were Escherichia coli (22.1%), Streptococcus uberis (19.1%) and coagulase-negative staphylococci (8.8%). In comparison, the main pathogen in multiparous cows with clinical mastitis at parturition was Staphylococcus aureus (11.2%).ConclusionMoving heifers to the calving facilities too late in tiestall farms increased risk for clinical mastitis at parturition. The isolated udder pathogens did not differ significantly in tiestall farms compared to freestall farms in heifers, but differences were found between heifers and multiparous cows at parturition.

Serological Evidence of Exposure to Globally Relevant Zoonotic Parasites in the Estonian Population.

We investigated Estonian population and its selected subgroups for serological evidence of exposure to Ascaris lumbricoides, Echinococcus spp., Taenia solium, Toxocara canis, Toxoplasma gondii, and Trichinella spiralis. Serum samples from 999 adults representing general population, 248 children aged 14–18, 158 veterinarians, 375 animal caretakers, and 144 hunters were tested for specific immunoglobulin G antibodies against the selected parasites using commercial enzyme immunoassays (ELISA). Sera yielding positive or twice grey zone Echinococcus spp, T. solium, T. canis, and T. spiralis results were subjected to western blot (WB) analysis. In the general population, based on the ELISA results, the A. lumbricoides seroprevalence was 12.7%, Echinococcus spp. seroprevalence was 3.3%, T. solium seroprevalence was 0.7%, T. canis seroprevalence was 12.1%, T. gondii seroprevalence was 55.8%, and T. spiralis seroprevalence was 3.1%. Ascaris lumbricoides seroprevalences were higher in children and in animal caretakers than in the general population, and T. canis seroprevalence was higher in animal caretakers than in the general population. Compared with the general population, Echinococcus spp. seroprevalence was higher in children. By contrast, T. gondii seroprevalence was higher in animal caretakers, and lower in children, than in the general population. In the general population, the WB-confirmed Echinococcus spp. seroprevalence was 0.5%, T. solium cysticercosis seroprevalence was 0.0%, Toxocara spp. seroprevalence was 14.5%, and Trichinella spp. seroprevalence was 2.7%. WB-confirmed Toxocara spp. seroprevalence was higher in animal caretakers than in the general population. We found serological evidence of exposure to zoonotic parasites in all tested groups. This calls for higher awareness of zoonotic parasitic infections in Estonia.

Neospora caninum in Estonian dairy herds in relation to herd size, reproduction parameters, bovine virus diarrhoea virus, and bovine herpes virus 1.

Cows infected with the tissue parasite Neospora caninum (Nc) are more likely to abort or give birth to calves with neurological disorders. The known infection routes are transplacentally and by consumption of oocysts shed by the definitive host, the dog. It has been hypothesised, that dormant stages of persistent Nc infection may be reactivated by immunosuppression mechanisms such as pathogenic invasions as bovine herpes virus 1 (BHV1) and bovine virus diarrhoea virus (BVDV). The study was set to give the first prevalence data on Nc from Estonian dairy herds in both animal as well as herd level. In addition, association between herd size and Nc, and association of Nc with abortion incidence (Ab), stillbirth incidence (Sb), insemination index (II), and calving interval (CaI) in the presence of BHV1 and BVDV was studied. Blood samples from 1973 animals from 100 herds were collected in 2006-2008, and 320 bulk tank milk (BTM) samples were collected in 2007. Antibodies against Nc was found in 2.5 ± 0.4% (95% CI) of the animals and at least one positive animal was found in 37.0 ± 4.7% (95% CI) of the herds. In addition, Nc antibodies were detected in 16.3 ± 2.0% (95% CI) of the tested BTM. Large herds (≥ 200 animals) were less likely to have seropositive animals for Nc. Logistic regression models showed that herds with more than one animal seropositive for Nc had significantly higher odds ratio of abortion incidence (OR: 11.92, 1.18-120.18 95% CI, p=0.036) and tendency of having more stillbirths (OR: 5.52, 0.87-35.02 95% CI, p=0.07). On the other hand one Nc seropostive cow in the herd was associated with lower odds ratio (OR: 0.22, 0.05-0.91 95% CI, p=0.04) of higher calving intervals. Estonian prevalence results reflect observations in the region. No evidence was found of the pathogens were affecting fertility variables through interactions but independently BHV1 and Nc had an impact on the abortion.

Toxoplasma gondii seroprevalence in dairy and beef cattle: Large-scale epidemiological study in Estonia

Toxoplasma gondii is a zoonotic protozoan parasite that thrives in Estonia. In this nationwide cross-sectional study, we tested sera from 3991 cattle, collected from 228 farms in 2012-2013, for anti-T. gondii immunoglobulin G antibodies using a commercial direct agglutination test. Titer of 100 was set as cut-off: samples that tested positive at the dilution 1:100 were defined as positive. The apparent animal-level seroprevalence was 18.62%. At least one seropositive animal was found on 68.86% of the farms, and seropositive cattle were detected in all counties. The seroprevalence appeared to increase with age until five years (60-71 months) of age, but had no obvious pattern in the older animals. Animals of the local Estonian Red breed had higher odds to test seropositive than did animals of the Estonian Holstein breed. Whether the farm focused on dairy or beef cattle was not associated with an animal testing T. gondii seropositive nor with finding at least one T. gondii seropositive animal on the farm. The odds of finding at least one T. gondii seropositive animal on the farm were higher if the herd size was above median (105 in dairy and mixed dairy farms; 35 in beef and mixed beef farms). The results indicate that T. gondii is endemic within the agricultural setting in Estonia and present on the majority of cattle farms.

Association of herd BHV-1 seroprevalence with respiratory disease in youngstock in Estonian dairy cattle

The associations between herd bovine herpesvirus 1 (BHV-1) seroprevalence, along with other infectious and farm management factors with bovine respiratory disease (BRD) in dairy calves and heifers, were investigated. Serum samples from 103 dairy cattle herds were analyzed for antibodies against BHV-1, bovine respiratory syncytial virus (BRSV), bovine viral diarrhea virus (BVDV), and Mycoplasma bovis (M. bovis). A questionnaire was used to record herd management practices. A high occurrence of respiratory disease in unweaned calves was associated with low to moderate and high prevalence of BHV-1 among cows (OR=14.8, p=0.005 and OR=19.2, p=0.002, respectively) and positive BVDV status of a herd (OR=5.1, p=0.02). The presence of BVDV in a herd was related to a high incidence of respiratory disease in heifers 3-16 months old (OR=4.3, p=0.027). Based on the results of multiple correspondence analysis, holding youngstock separately from cows until pregnancy, introducing new animals and the activities of on-farm employees may contribute to a higher incidence of BRD.

Epidemiology, risk factors and varroa mite control in the Estonian honey bee population

This is the first large scale study demonstrating the status of varroa infestation and control and related risk factors in Estonian apiaries. Colonies in one hundred and ninety-six apiaries were sampled during 2012–2013. A questionnaire was used to record management, as well as treatment procedures applied. The majority of apiaries sampled (98.5, 95% CI = 95.6; 99.7%) were infested with varroa mites and the mean proportion of affected colonies within apiaries was high (78.9, 95% CI 77.2; 80.6%). Apiary median colony infestation level was 2 mites per 300 bees (mean 4.5, range 0–25). According to multivariable random-effect logistic regression analysis, the numbers of colonies in an apiary (OR = 1.04, 95% CI 1.01; 1.06, p = 0.004) and the presence of a hybrid breed of bees (OR = 2.22, 95% CI 0.88; 5.61, p = 0.093) were associated with higher risk of colony varroa infestation. Apiary management by a professional beekeeper (OR = 0.38, 95% CI 0.15; 0.97, p = 0.044), bees of the Buckfast breed (OR = 0.36, 95% CI 0.11; 1.13, p = 0.079), synchronized treatments between neighboring beekeepers (OR = 0.34, 95% CI 0.16; 0.68, p = 0.003) and the presence of farmland around the apiary (OR = 0.29, 95% CI 0.09; 0.95, p = 0.041) were factors protective against colony varroa infestation. Varroa treatment was applied in 93% of the studied apiaries. Chemical and organic substances were used by 66 and 61% of beekeepers, respectively in 2012.

Effect of vaccination against bovine herpesvirus 1 with inactivated gE-negative marker vaccines on the health of dairy cattle herds

The aim of this study was to estimate the effect of the bovine herpesvirus 1 (BHV-1) vaccination on herd health and production in BHV-1 infected Estonian dairy cattle herds. Seven herds vaccinated with inactivated gE-negative BHV-1 marker vaccines and seven matched non-vaccinated herds were selected. In vaccinated herds the calving interval was on average 7.01 days shorter compared to that in the non-vaccinated herds (coef=-7.01, 95% CI=-11.98, -2.03, p=0.008) during the study period (2007-2012). In non-vaccinated herds the insemination index had an increasing trend (coef(log scale)=0.03, 95% CI=-0.003, 0.06, p=0.054) and the first service conception rate decreased (coef=-2.19, 95% CI=-3.91, -0.47, p=0.015), whereas no significant changes occurred in vaccinated herds. Average yearly milk yield per cow increased (coef=145.30, 95% CI=-6.11, 296.71, p=0.065) and length of the dry period decreased in BHV-1 vaccinated herds (coef(log scale)=-0.02, 95% CI=-0.04, 0.004, p=0.056) compared to non-vaccinated herds during the study years. Youngstock and the cow culling rate due to respiratory disease was significantly lower in vaccinated herds compared to non-vaccinated herds (coef=-0.29, 95% CI=-0.47, -0.11, p=0.003 and coef=-0.15, 95% CI=-0.29, -0.007, p=0.043, respectively). These results suggest that vaccination against BHV-1 is associated with herd health and productivity.