A longitudinal study of disease incidence and case-fatality risks on small-holder dairy farms in coastal Kenya

A longitudinal study was carried out in the coastal lowlands coconut-cassava agro-ecological zone of Kaloleni Division, Coast Province, Kenya between June 1990 and December 1991 to estimate disease incidence and cause-specific case-fatality risk in an average of 120 cattle in 26 small-holder dairy herds kept in two grazing-management systems. East Coast fever (ECF) was the predominant disease diagnosed; the mean monthly incidence rate was 2.5 and 6.9% in animals < or = 18 months of age under stall-fed and herded-grazing systems, respectively. In cattle > 18 months of age, the monthly incidence rate was < 1%. The 6-month ECF incidence rate was 20+/-8% (S.E.) in the stall-feeding system compared with 39+/-7% in the herded-grazing systems. There was a gradual increase in antibody prevalence with age to over 90% in cattle over 18 months of age in herded-grazing systems, whilst less than a third of cattle in the stall-feeding systems were sero-positive at any age. Overall accumulated mortality to 18 months of age was estimated to be 56%. Annual mortality in cattle > 18 months averaged 9%. Cattle managed in the herded-grazing system had a 60% higher mortality, although not significantly so, than those fed in stalls. Deaths due to ECF accounted for over two-thirds of the deaths. ECF was then the major disease constraint to small-holder dairy production in the coconut zone of coastal Kenya. Clinical cases occur the whole year round (especially in young stock)--despite apparent tick control, and in both herded-grazing and stall-feeding system.     

Identification of a target population for immunisation against East Coast fever in coastal Kenya

Two experiments were carried out to identify the target population of cattle for immunisation against East Coast fever (ECF) using the infection-and-treatment method. Firstly, a sentinel-calf study was used to determine the age window for ECF immunisation by determining ages at clinical detection of infection with Theileria parva. Six groups of five naive cross-bred (Bos taurus/Bos indicus) male calves, introduced at intervals of 2 months at a mean age of 26 days, were exposed to natural tick challenge on a high ECF-risk, small-holder farm in the coastal lowland, coconut-cassava agro-ecological zone of coastal Kenya. Secondly, a challenge study evaluated the relationship between the presence of T. parva antibodies and immunity. Ten indigenous adult Zebu cattle and nine Zebu young stock purchased from farmers in the same zone, and eight cross-bred calves (survivors of the sentinel-calf study) were challenged with 10 times the immunising dose of T. parva Marikebuni stock. Twenty-four of these 27 cattle had high antibody titres before challenge. Two cross-bred calves, obtained from an ECF-free area and seronegative to T. parva schizont antigen, also were challenged and used as susceptible controls. Twenty-five (83%) of the 30 sentinel calves contracted ECF over an age range of 36-116 days (mean 72 days). The remaining five calves died of other causes within 2 months of arrival on the farm. Fourteen of the 25 calves survived the infection and developed antibodies to T. parva. Despite tick control, seven of these 14 calves had a second episode of ECF and two died. In total, 13 of the 25 calves that contracted ECF died. Only one of 19 indigenous Zebu animals developed clinical ECF when challenged with T. parva Marikebuni (mild clinical signs with spontaneous recovery). Of the eight cross-bred survivors from the first experiment, only one succumbed to ECF when challenged and it died. Both susceptible cross-bred calves developed severe clinical signs of ECF and one died. The experimental studies show that in the high ECF-risk areas of the coconut-cassava zone of coastal Kenya, immunisation against ECF in cross-bred (B. taurus/B. indicus) cattle should be targeted at an early age (preferably within 1-2 months of birth).     

Risk of babesiosis and anaplasmosis in different ecological zones of Santa Cruz Department, Bolivia

A cross-sectional study was done of seroprevalence of Babesia bigemina, B.bovis, and Anaplasma marginale in cattle from eastern Bolivia, to characterise the risk of tick-borne disease in three ecological zones. Nineteen farms were sampled in the subtropical humid zone, 13 in the dry subtropical zone and nine in the lower western valleys of the Andean massif. The enzyme-linked immunosorbent assay was used. All three pathogens were widespread. For B. bovis, seroprevalences were high (75-78%) in the two subtropical zones which thus had low risk of disease from this infection; but the western valleys were endemically unstable with higher risk. For B. bigemina, seroprevalences were lower (24-57%) in the two subtropical zones and thus these areas were endemically unstable for disease from this infection. However, the seroprevalence of B. bigemina in the western valleys was too low (13%) for risk of disease in susceptible cattle to be considered high. For A. marginale, the seroprevalences in the two subtropical zones were low (19-32%) and very low (6%) in the western valleys suggesting all these zones were endemically unstable for anaplasmosis. Data for individual farms were analysed for risk of both forms of babesiosis; this showed low risk of disease in the subtropical humid zone, higher risk in the dry subtropical zone and variable risk in the western valleys.     

Clinical features associated with seroconversion to Anaplasma marginale, Babesia bigemina and Theileria parva infections in African cattle under natural tick challenge

A longitudinal study was conducted in Southeast Uganda for 14 months on 640 Zebu cattle kept under natural tick challenge, with a view to identifying clinical features for prediction of seroconversion to Anaplasma marginale, Babesia bigemina and Theileria parva infections. Physical examination, condition scoring and tick counts were undertaken on all cattle every 4 weeks. In addition, 5300 sera were collected and analysed for antibodies against A. marginale, B. bigemina and T. parva infections using the enzyme-linked immunosorbent assay (ELISA). The major clinical features compiled included weight loss, fever (rectal temperature), anaemia (packed cell volume), pallor of mucous membranes, lymph node enlargement, staring coat, diarrhoea and lacrymation. The risk factors included tick challenge at village level, sex, age, Rhipicephalus spp. density and Boophilus spp. density on individual animals. Using a binary logistic regression model, the clinical features and risk factors were analysed. The results suggest that increasing rectal temperature was associated with increased probability for seroconversion to A. marginale, while high level of Rhipicephalus spp. density and increasing packed cell volume (PCV) were significantly associated with reduced probability of seroconversion. Although statistically significant, none of the factors had large effects, with odds ratios (OR) of 0.87, 1.15 and 0.98 for Rhipicephalus spp. density, rectal temperature and PCV, respectively. For B. bigemina infection, a high level of Boophilus spp. density, anaemia and staring coat were significantly associated with increased probability of seroconversion (OR 1.50, 1.78, 1.37, respectively). Presence of lacrymation and old age were associated with reduced probability of seroconversion (OR 0.52, 0.86 respectively). For T. parva infection, lymph node enlargement (OR 1.30) was associated with increased probability of seroconversion, while high Rhipicephalus spp. density and increasing packed cell volume (PCV) were associated with reduced probability of seroconversion (OR 0.68 and 0.98, respectively). In conclusion, presence and intensity of the respective tick vectors for tick-borne diseases, age and clinical features such as anaemia, fever, staring coat, lymph node enlargement and lacrymation are indicators for seroconversion to A. marginale, B. bigemina and T. parva infections in cattle. These indicators for seroconversion could be exploited in the development of decision support tools for clinical diagnosis of tick-borne diseases.     

Prevalence of serum antibodies to Mycobacterium avium subsp. paratuberculosis in cattle in Galicia (northwest Spain)

Prior to establishing a control and prevention program for Johne's disease in cattle in Galicia (northwest Spain), a survey was conducted to estimate the prevalence of the disease. For this survey, 61,069 animals of at least 1-year of age from 2735 randomly selected herds were bled and samples analyzed with a commercial ELISA. The estimated true individual-level prevalences – assuming the manufacturer's reported test sensitivity of 48.5% and specificity of 98.9% – were 3.02% in dairy cattle, 1.03% in beef cattle and 2.83% in animals from farms with both dairy and beef cattle. True herd prevalences (with herds declared positive if one or more animals tested positive) were 10.69% for dairy herds, 0% for beef herds and 2.71% for mixed herds. When herds were declared positive if at least two animals tested positive, true herd prevalences were 14.75% for dairy herds, 1.47% for beef herds and 12.01% for mixed herds. Assuming a higher specificity of 99.4%, true individual-level prevalences increased to 4.03% in dairy herds, 2.07% in beef herds and 3.84% in mixed herds. Herd prevalences were 27.77%/18.79%, 2.78%/2.40% and 5.70%/12.24% (using the one/two-animal cut-offs) in dairy, beef and mixed herds, respectively. In conclusion, these results seem to indicate that a small percentage of cows and a rather high percentage of dairy herds in this region are MAP-seropositive.     

Exploratory spatial data analysis of regional seroprevalence of antibodies against epizootic hemorrhagic disease virus in cattle from Illinois and Indiana

OBJECTIVE: To estimate seroprevalence of antibodies against the serogroup of epizootic hemorrhagic disease viruses (EHDVs) and describe spatial distribution of antibodies against EHDV among cattle herds in Illinois and western Indiana. SAMPLE POPULATION: 9,414 serum samples collected from cattle in 60 herds over 3 transmission seasons. PROCEDURES: Serum samples were tested for antibodies against EHDV by use of an ELISA. Seroprevalence for 4 zones covering the length of Illinois and parts of Indiana were estimated. A multivariable mixed-effects logistic regression model with a random effect for herd was used to estimate seropositive risk for zone (1 through 4), age (yearling, adult), herd type (beef, dairy), transmission season (2000 to 2002), and zone by year interaction. Isopleth maps of seroprevalence at the herd level were produced. RESULTS: Antibodies against EHDV were detected in 1,110 (11.8%) samples. Estimated seroprevalence in 2000, 2001, and 2002 was 15.3%, 13.4%, and 5.2%, respectively. Seroprevalence was highest in the southernmost zone and lowest in the northernmost zone, but risk of seropositivity for EHDV among and within zones varied by year. Clusters of high seroprevalence in the south, low seroprevalence in the north, and outliers of high and low seroprevalence were detected. Risk mapping revealed areas of higher seroprevalence extending northward along the western and eastern ends of the study region. CONCLUSIONS: Seroprevalence of antibodies against EHDV in cattle was higher in the south than north; however, local complexities existed that were not observed in a serosurvey of antibodies against bluetongue virus from the same cattle population.     

Epidemiology of tick-borne diseases of cattle in Botshabelo and Thaba Nchu in the Free State Province

A seroepidemiological study was conducted on 151 cattle from the Botshabelo and Thaba Nchu areas in the central Free State Province of South Africa, two areas where small scale, peri-urban cattle farming is practised. An indirect fluorescent antibody test was used to test for Babesia bigemina and B. bovis antibodies. To test for Anaplasma marginale antibodies a competitive inhibition enzyme-linked immunosorbent assay method was used. There were no significant differences in serological test results between the cattle from Botshabelo and those from Thaba Nchu. The herd (two areas combined) had an average seroprevalence of 62.42% to B. bigemina, 19.47% to B. bovis and 98.60% to A. marginale. Based on the percentage of cattle that were seropositive to B. bigemina the immune status of cattle in the Botshabelo-Thaba Nchu area is approaching a situation of endemic stability. With reference to A. marginale, the high seroprevalence is indicative of a situation of endemic stability. The occurrence of B. bovis antibodies in the cattle is difficult to explain as Boophilus microplus ticks do not occur in the area in which the study was conducted.     

Productivity and health effects of anaplasmosis and babesiosis on Bos indicus cattle and their crosses, and the effects of differing intensity of tick control in Australia

Tick fever is an important disease of cattle where Rhipicephalus (Boophilus) microplus acts as a vector for the three causal organisms Babesia bovis, Babesia bigemina and Anaplasma marginale. Bos indicus cattle and their crosses are more resistant to the clinical effects of infection with B. bovis and B. bigemina than are Bos taurus cattle. Resistance is not complete, however, and herds of B. indicus-cross cattle are still at risk of babesiosis in environments where exposure to B. bovis is light in most years but occasionally high. The susceptibility of B. indicus cattle and their crosses to infection with A. marginale is similar to that of B. taurus cattle. In herds of B. indicus cattle and their crosses the infection rate of Babesia spp. and A. marginale is lowered because fewer ticks are likely to attach per day due to reduced numbers of ticks in the field (long-term effect on population, arising from high host resistance) and because a smaller proportion of ticks that do develop to feed on infected cattle will in turn be infected (due to lower parasitaemia). As a consequence, herds of B. indicus cattle are less likely than herds of B. taurus cattle to have high levels of population immunity to babesiosis or anaplasmosis. The effects of acaricide application on the probability of clinical disease due to anaplasmosis and babesiosis are unpredictable and dependent on the prevalence of infection in ticks and in cattle at the time of application. Attempting to manipulate population immunity through the toleration of specific threshold numbers of ticks with the aim of controlling tick fever is not reliable and the justification for acaricide application should be for the control of ticks rather than for tick fever. Vaccination of B. indicus cattle and their crosses is advisable in all areas where ticks exist, although vaccination against B. bigemina is probably not essential in pure B. indicus animals.     

Prevalence and genetic diversity of Babesia and Anaplasma species in cattle in Sudan

Disease prevalence studies are one of the most valuable tools to demonstrate the risk or impact of certain infections in local and global economies. The data obtained in these studies contribute to develop strategies for disease control. The present study aims to provide information about the prevalence of babesiosis and anaplasmosis in the northern regions of Sudan. Blood samples from four different states of Sudan were collected from apparently healthy cattle (n=692), DNA was extracted and the prevalence of Babesia and Anaplasma species was analyzed by PCR. The results confirmed the presence of Babesia bigemina, Babesia bovis and Anaplasma marginale in cattle in northern Sudan with overall prevalence rates of 4.0%, 1.9% and 6.1%, respectively. Statistical analysis revealed that the prevalence of B. bigemina, B. bovis and A. marginale varies significantly between Sudanese states as well as in different age groups, while gender seems not to have a significant effect on the prevalence of these pathogens among Sudanese cattle. The highest prevalence for B. bigemina was found in the Aljazirah State while the highest number of A. marginale positive samples was reported in River Nile.     

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.     

Mass screening of cattle sera against 14 infectious disease agents, using an ELISA system for monitoring health in livestock.

Mass screening ELISA methods were developed for testing cattle serum for antibodies against 14 common livestock diseases simultaneously. The absorbance values were transformed to a %ELISA (spectrophotometric antibody end point) by a computer interfaced with a microplate reader. A histogram indicating a cutoff point and a report for the veterinarian also was generated. The computer program produced a print-out of the antibody profile for each animal tested, the antibody concentration against each disease, and a histogram (antibody profile) showing the prevalence of each disease in the herd. Serum samples were obtained from 1,953 cattle, including 880 dairy cattle from 10 herds and 1,073 beef cattle from 20 herds. These samples were obtained from June 1988 through June 1989. The highest antibody prevalence was against bluetongue virus. Of the 1,953 cattle tested, 1,223 (63%) were seropositive for bluetongue virus, including 502 (57%) of the dairy cattle and 721 (67%) beef cattle. Other antibody prevalences, in descending order, were: rotavirus (44%), Pasteurella spp (25%), Leptospira spp and Haemophilus spp (22%), Mycoplasma spp (18%), parainfluenza virus (17%), Campylobacter spp (16%), Anaplasma marginale (15%), bovine leukosis virus (13%), Brucella spp (8%), Mycobacterium paratuberculosis (8%), bovine viral diarrhea virus (3%), and infectious bovine rhinotracheitis virus (3%). Major differences in antibody prevalence between dairy and beef cattle were that only 4% of the dairy cattle were seropositive for A marginale, compared with 25% of the beef cattle, and conversely, 29% of the dairy cattle were seropositive for bovine leukosis virus, compared with 1% of the beef cattle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prevalence and molecular detection of Anaplasma marginale, Babesia bovis and Babesia bigemina in cattle from Puntarenas Province, Costa Rica

A study was conducted in 2008 to determine the prevalence of Anaplasma and Babesia infections in cattle in the Puntarenas Province of Costa Rica. Blood samples were taken from a total of 449 cattle during the month of March at 30 farms in the region of Espiritu Santu, Costa Rica. Commercially available enzyme-linked immunosorbent assays (ELISA) were used to determine presence of antibodies to Babesia bigemina and Anaplasma marginale, and real-time PCR was used to determine the presence of DNA from the disease-causing organisms. The ELISA results indicated that 87.5% of the cattle sampled were positive for antibodies to A. marginale, while 59.1% were positive for antibodies to B. bigemina. The real-time PCR results showed that 235 cattle were carrying A. marginale DNA (56.9%), 6 with B. bigemina DNA (1.34%), and 2 with B. bovis DNA (0.45%).     

Seroprevalence of Babesia bovis and Babesia bigemina in cattle in the Soutpansberg region, Limpopo Province, South Africa, associated with changes in vector-tick populations

A survey was conducted at 30 communal dip tanks and on 5 commercial farms in Limpopo Province, South Africa, during 1999 and 2000 to determine the seroprevalence of antibodies to Babesia bovis and Babesia bigemina. Cattle seropositive for B. bovis were found in 97% of the herds on communal land; the overall seroprevalence changed little between 1999 (63.3%) and 2000 (62.4%). All herds surveyed were infected with B. bigemina, and overall seroprevalence decreased significantly from 56.1% in 1999 to 49.3% in 2000. In herds on communal land in Sour Lowveld Bushveld, overall seroprevalence of B. bovis increased from 70% in 1999 to 80% in 2000, while seroprevalence of B. bigemina decreased from 70% in 1999 to 30% in 2000. This was possibly due to an influx of Rhipicephalus (Boophilus) microplus that occurred at the time. In commercially farmed herds the seroprevalence to B. bovis increased significantly from 19% in 1999 to 57.5% in 2000. All commercial herds in the survey tested positive to B. bigemina, with a seroprevalence of 48.3% in 1999 and 47.5% in 2000. During 1999, cattle in 60% of the dip tank/farm herds with only R. (B.) microplus present were approaching endemic stability to both B. bovis and B. bigemina. In 2000, 60% of the herds with only R. (B.) microplus present were approaching endemic stability for B. bovis, while only 45% were approaching endemic stability for B. bigemina. Those dip tanks/farms where only R. (B.) microplus was recorded had a significantly higher seroprevalence of B. bovis than those where both tick species were present.     

Epidemiology of bovine anaplasmosis in dairy herds from Costa Rica

Bovine anaplasmosis is endemic and occurs in almost all areas of livestock production of Costa Rica. The aim of this study was to determine the seroprevalence and risk factors of anaplasmosis in dairy farms of Costa Rica by the recombinant truncated MSP-5 (rMSP-5) enzyme-linked immunosorbent assay (ELISA). Serum samples were obtained from 733 cattle from 20 commercial dairy herds of Costa Rica. The overall seroprevalence was 37.2% and herd seroprevalence ranged from 20.0 to 72.0%. The age-specific seroprevalence was 49.3% in young and 33.4% in adult animals. The main risk factors associated with seroprevalence were season of occurrence of clinical cases (rainy season) (OR=22.8), presence of tabanids (OR=9.5) and stable flies (OR=6.2), stable flies control measures (OR=3.2), non-use of ear tattoos (OR=2.8), interval of veterinary visit (≤ 60 days) (OR=2.7), altitude of the farms (<800 masl) (OR=2.6) and age (<2 years) (OR=1.8). The results indicated that exposure of cattle to Anaplasma marginale is common in dairy herds of Costa Rica and endemic instability situation probably is due to inadequate vector control.     

Supranational comparison of Neospora caninum seroprevalences in cattle in Germany, The Netherlands, Spain and Sweden

Herd, within-herd and animal prevalences for Neospora caninum in beef and dairy cattle were compared between four countries. In randomly selected herds from regions of Germany, The Netherlands, Spain and Sweden that were representative for the cattle production of these countries, all animals > or = 2 years were examined serologically by enzyme-linked immunosorbent assays (ELISAs) with high test specificity (> 98.0%). In a previous study, the ELISAs had been validated against each other. Single reacting animals within a herd were confirmed by immunobloting. At the time of sampling, animal (age, breed, herdtype, sex, lactation stage) and herd data (region) were collected. Considerable differences in N. caninum herd, within-herd, and overall animal prevalence estimations were observed between countries, regions, herdtype, age categories and breeds. Herd prevalences, based on confirmation of single reactors, for dairy herds were estimated to be 16% (95%CI: 10-24%) in Sweden, 49% (95%CI: 39-59%) in Germany, 63% (95%CI: 57-69%) in Spain and 76% (95%CI: 67-84%) in The Netherlands and for beef herds 41% (95%CI: 31-50%) in Germany, 46% (95%CI: 41-51%) in Spain and 61% (95%CI: 50-72%) in The Netherlands. No beef herds were examined in Sweden. The lowest animal true prevalence was estimated in dairy cattle in Sweden (0.5% (95%CI: 0.1-0.8%)) while the highest animal true prevalence was estimated for dairy cattle in Spain (16.2% (95%CI: 14.9-17.5%)). Within-herd prevalences varied greatly, with very few farms in Sweden having more than 10% seropositive animals while in Spain more than 10% of the herds had within-herd prevalences between 50 and 100%. Seropositivity was significantly associated with herdtype (beef versus dairy), age, breed and region within countries. The results of this supranational comparative study showed that the importance of N. caninum infection varied greatly within in Europe. Estimates of prevalence can be used to calculate the economic impact of N. caninum infection as well as to evaluate the effect of prevention and control strategies over time.     

Prevalence of lameness among dairy cattle in Wisconsin as a function of housing type and stall surface

OBJECTIVE: To determine the prevalence of lameness as a function of season (summer vs winter), housing type (free stalls vs tie stalls), and stall surface (sand vs any other surface) among lactating dairy cows in Wisconsin. DESIGN: Epidemiologic survey. ANIMALS: 3,621 lactating dairy cows in 30 herds. PROCEDURE: Herds were visited once during the summer and once during the winter, and a locomotion score ranging from 1 (no gait abnormality) to 4 (severe lameness) was assigned to all lactating cows. Cows with a score of 3 or 4 were considered to be clinically lame. RESULTS: Mean +/- SD herd lameness prevalence was 21.1 +/- 10.5% during the summer and 23.9 +/- 10.7% during the winter; these values were significantly different. During the winter, mean prevalence of lameness in free-stall herds with non-sand stall surfaces (33.7%) was significantly higher than prevalences in free-stall herds with sand stall surfaces (21.2%), tie-stall herds with non-sand stall surfaces (21.7%), and tie-stall herds with sand stall surfaces (12.1%). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the prevalence of lameness among dairy cattle in Wisconsin is higher than previously thought and that lameness prevalence is associated with season, housing type, and stall surface.     

Neospora caninum seroprevalence in dairy and beef cattle from the northwest region of Spain, Galicia

Herd and individual animal seroprevalence for Neospora caninum (N. caninum) in dairy, beef and mixed cattle were obtained in all populations within the Galician Farmer Sanitary Defence Associations (ADSG) in 2004. All animals ≥1 year of age were examined serologically by indirect ELISA. 1147 dairy herds (37,090 animals), 1464 beef herds (20,206 animals) and 141 mixed herds (2292 animals) were surveyed. True herd seroprevalence was estimated to be 80.6% (87.7% dairy, 76.7% beef and 78.4% mixed herds), true animal seroprevalence was estimated to be 23.2% (21.9% dairy, 25.1% beef and 24.9% animal to mixed herds), and within-herd seroprevalence was estimated to be 25.4% (23.6% dairy, 28.3% beef and 28.6% to mixed herds). Seropositivity was significantly associated with herd type (higher in dairies), herd size (increased when herd size increases), animal type (higher in beef) and age (lineal increase with the age). Results obtained in this study will be used for the development of a N. caninum control programme in the ADSG in Galicia.     

Genetic diversity of Anaplasma marginale strains from cattle farms in the province of Palermo, Sicily

Bovine anaplasmosis, caused by the tick-borne rickettsia Anaplasma marginale, is endemic in Sicily and results in economic loss to the cattle industry. This study was designed to characterize strains of A. marginale at the molecular level from cattle in the Province of Palermo, Sicily. Seropositivity of cattle >or=1 year old for A. marginale in the study area ranged from 62% to 100%. The observed prevalence of A. marginale infections in cattle herds ranged from 25% to 100%. Two predominant A. marginale msp4 genotypes were found. A positive correlation was found between the prevalence of infection and the presence of Rhipicephalus (Boophilus) annulatus. Phylogenetic analysis of msp4 sequences of European strains of A. marginale did not provide phylogeographical information. These results suggest that development of farm husbandry systems and vaccines for genetically heterogeneous populations of A. marginale are needed for control of anaplasmosis in this region of Sicily.     

A longitudinal study of sero-conversion to tick-borne pathogens in smallholder dairy youngstock in Tanzania

A longitudinal study of sero-conversion of youngstock to the tick-borne pathogens Theileria parva, T. mutans, Anaplasma marginale, Babesia bigemina and B. bovis was conducted over two years on smallholder dairy farms in Tanga region, Tanzania. There was evidence of maternal antibodies to all tick-borne pathogens in animals less than 18 weeks of age. Seroprevalence increased as expected with age in animals older than this but seroprevalence profiles underestimated the force of infection due to waning antibody levels between samplings. By the end of the 2-year study, less than 50% of study animals had seroconverted to each of the tick-borne pathogens investigated, consistent with the low levels of tick attachment observed on the study animals. Some associations between seroconversion to tick-borne pathogens, and counts of their known tick vectors on the animals, were identified as expected. However, some were not, suggesting that counts of some tick species may act as an index of rates of attachment of other vector species. Variation in acaricide treatment frequencies was not associated with variations in tick-borne pathogen seroprevalence suggesting that acaricides may be used more frequently than necessary on many farms. Most animals were zero-grazed, a management system associated with a significantly lower likelihood that animals seroconverted to any tick-borne pathogen except A. marginale. Seroprevalence varied locally with farm location (particularly for Babesia spp.) but was not well predicted by indices of ecological conditions. Our findings suggest that attempts to achieve a state of 'endemic stability' for tick-borne pathogens may be unreasonable on the smallholder dairy farms studied but reductions in the frequency of use of acaricides may be possible following prospective studies of effects on mortality and morbidity due to tick-borne pathogens.     

Prevalence and risk factors associated with bovine viral diarrhea virus infection in dairy herds in Jordan

A cross-sectional study was carried out to determine the seroprevalence and to identify risk factors associated with bovine viral diarrhea virus (BVDV) infection in 62 non-vaccinated dairy herds (671 cows) in Jordan between January and June 2007. Information regarding herd management was recorded through a personal interview with farmers. Antibodies against BVDV were detected using an indirect ELISA test. Chi-square analysis and multivariable logistic regression model were used to identify risk factors for BVDV seropositivity. The true prevalence of antibodies against BVDV in individual cows and cattle herds was 31.6% and 80.7%, respectively. The seroprevalence of BVDV in medium and large size herds was significantly higher than that in smaller herds. There was no significant difference in BVD seroprevalence between different age groups. Random-effects logistic regression model revealed two major factors associated with seropositivity to BVDV; exchange of visits between adjacent farm workers and not isolating newly purchased animals before addition to the herd. The seroprevalence of BVDV in cows located in the northern Jordanian governorates was significantly higher than that in other studied governorates. Results of this study indicated that BVDV is highly prevalent in Jordan and BVDV infection could be controlled by livestock-trade control, and applying strict biosecurity measures in the dairy farms.