Simulating the impact of four control strategies on the population dynamics of Neospora caninum infection in Swiss dairy cattle

A dynamic deterministic simulation model was developed to assess the impact of different putative control strategies on the seroprevalence of Neospora caninum in female Swiss dairy cattle. The model structure comprised compartments of “susceptible” and “infected” animals (SI-model) and the cattle population was divided into 12 age classes. A reference model (Model 1) was developed to simulate the current (status quo) situation (present seroprevalence in Switzerland 12%), taking into account available demographic and seroprevalence data of Switzerland. Model 1 was modified to represent four putative control strategies: testing and culling of seropositive animals (Model 2), discontinued breeding with offspring from seropositive cows (Model 3), chemotherapeutic treatment of calves from seropositive cows (Model 4), and vaccination of susceptible and infected animals (Model 5). Models 2–4 considered different sub-scenarios with regard to the frequency of diagnostic testing. Multivariable Monte Carlo sensitivity analysis was used to assess the impact of uncertainty in input parameters.

A policy of annual testing and culling of all seropositive cattle in the population reduced the seroprevalence effectively and rapidly from 12% to <1% in the first year of simulation. The control strategies with discontinued breeding with offspring from all seropositive cows, chemotherapy of calves and vaccination of all cattle reduced the prevalence more slowly than culling but were still very effective (reduction of prevalence below 2% within 11, 23 and 3 years of simulation, respectively). However, sensitivity analyses revealed that the effectiveness of these strategies depended strongly on the quality of the input parameters used, such as the horizontal and vertical transmission factors, the sensitivity of the diagnostic test and the efficacy of medication and vaccination. Finally, all models confirmed that it was not possible to completely eradicate N. caninum as long as the horizontal transmission process was not interrupted.     

Effectiveness of vaccines and vaccination programs for the control of foot-and-mouth disease in Uganda, 2001–2010

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals. In Uganda, FMD outbreaks are mainly controlled by ring vaccination and restriction of animal movements. Vaccination stimulates immunity and prevents animals from developing clinical signs which include lameness, inappetence, and decreased production. Ring vaccination and restriction of animal movements have, however, not successfully controlled FMD in Uganda and outbreaks reoccur annually. The objective of this study was to review the use of FMD virus (FMDV) vaccines and assess the effectiveness of vaccination programs for controlling FMD in Uganda (2001–2010), using retrospective data. FMD vaccine distribution patterns in Uganda (2001–2010) matched occurrence of outbreaks with districts reporting the highest number of outbreaks also receiving the largest quantity of vaccines. This was possibly due to “fire brigade” response of vaccinating animals after outbreaks have been reported. On average, only 10.3 % of cattle within districts that reported outbreaks during the study period were vaccinated. The average minimum time between onset of outbreaks and vaccination was 7.5 weeks, while the annual cost of FMDV vaccines used ranged from US $58,000 to 1,088,820. Between 2001 and 2010, serotyping of FMD virus was done in only 9/121 FMD outbreaks, and there is no evidence that vaccine matching or vaccine potency tests have been done in Uganda. The probability of FMDV vaccine and outbreak mismatch, the delayed response to outbreaks through vaccination, and the high costs associated with importation of FMDV vaccines could be reduced if virus serotyping and subtyping as well as vaccine matching were regularly done, and the results were considered for vaccine manufacture.     

Financial analysis of various strategies for the control of Neospora caninum in dairy cattle in Switzerland

The present study was conducted to estimate the direct losses due to Neospora caninum in Swiss dairy cattle and to assess the costs and benefits of different potential control strategies. A Monte Carlo simulation spreadsheet module was developed to estimate the direct costs caused by N. caninum, with and without control strategies, and to estimate the costs of these control strategies in a financial analysis. The control strategies considered were “testing and culling of seropositive female cattle”, “discontinued breeding with offspring from seropositive cows”, “chemotherapeutical treatment of female offspring” and “vaccination of all female cattle”. Each parameter in the module that was considered to be uncertain, was described using probability distributions. The simulations were run with 20,000 iterations over a time period of 25 years.

The median annual losses due to N. caninum in the Swiss dairy cow population were estimated to be € 9.7 million. All control strategies that required yearly serological testing of all cattle in the population produced high costs and thus were not financially profitable. Among the other control strategies, two showed benefit–cost ratios (BCR) >1 and positive net present values (NPV): “Discontinued breeding with offspring from seropositive cows” (BCR = 1.29, NPV = € 25 million) and “chemotherapeutical treatment of all female offspring” (BCR = 2.95, NPV = € 59 million). In economic terms, the best control strategy currently available would therefore be “discontinued breeding with offspring from seropositive cows”.     

Management factors associated with Babesia bovis seroprevalence in cattle from eastern Yucatán, Mexico.

The effect of management on the seroprevalence of Babesia bovis was studied in 399 Bos indicus cattle 1–2 years old from 92 farms in the eastern Yucatán, México. The management factors studied were: farm-type, production system, herd size, farm size, stocking density, vector control, dipping interval, type of dipping, type of acaricide and cattle introduction to the farm. A cross-sectional study was carried out (2-stage cluster sampling). The number of serum samples was proportionally distributed according to the number of farms in the nine locations of eastern Yucatán, México (399 animals from 92 farms). Antibody activity to B. bovis was tested using an indirect ELISA. The farms with a seroprevalence ≤75% were considered as cases and those with seroprevalence >75% were considered as controls. The variables with p ≤ 0.20 were included in fixed effects logistic regression. The seroprevalence of the zone was 73.8% (66.3–81.3%). The following risk factors were found: Stocking density (<1 head/ha, OR = 4.04, CI (OR) = 1.20–13.62) and dipping interval (>60 days, OR = 5.07 CI (OR) = 1.26–20.48).     

A case-control study of risk factors for brucellosis seropositivity in Portuguese small ruminants herds

A case–control study involving 255 small ruminants herds randomly selected was carried out in Portugal between January and December 2004, to identify risk factors associated with brucellosis seropositivity.

To achieve this objective, two groups of herds selected according their prevalence status were compared: “cases” (farms with seroprevalence higher than 5%, n = 123) and “controls” (farms seronegatives, n = 132). A carefully structured questionnaire was used to collect data from each herd. A statistical analysis to compare “case” versus “control” herds was performed with the variables obtained from the questionnaire and the seroprevalence results. The effects on seroprevalence of several variables such as: individual characteristics; farm management practices; farm characteristics; animal health; knowledge and characteristics of farmers were evaluated. Data were analysed using logistic regression. Univariable analysis was used to screen the variables used in the logistic regression model. Nine variables were associated with brucellosis seropositivity in univariable analysis p < 0.10. These variables were retained for multivariable logistic regression model. Regression model identified five variables as risk factors for seropositivity. The odds of brucellosis were increased: herds with more than 116 animals (OR = 2.99); in herds with no cleaned-watering places (OR = 3.05); in herds with insufficient manure removal and insufficient cleaning of premises (OR = 2.87); in introduction of animals from non-free brucellosis herds or from herds of unknown status (OR = 12.11). In the other hand, farmers’ age (the eldest) was related to decreased odds (OR = 0.4).

Potential risk factors identified in this study were consistent factors associated with brucellosis seropositivity and support current recommendations for the control of brucellosis. Considering the paucity of epidemiological reports on brucellosis in the Northeast of Portugal and the absence of any data concerning factors related to either the prevention or the spread of the disease, our results could make a useful contribution towards the prevention of small ruminants brucellosis in the area.     

Seroprevalence of chlamydial infection in dairy cattle in Guangzhou, southern China

Chlamydia spp. are obligate intracellular gram-negative bacteria that cause a wide range of significant diseases in humans and animals worldwide, resulting in significant economic losses. Chlamydial infection in cattle has been reported in many countries including China. However, there has been no survey of chlamydial infection of dairy cattle in Guangzhou, southern China. The objective of the present investigation was to examine the chlamydial seroprevalence in dairy cattle in Guangzhou, subtropical southern China by using an indirect hemagglutination assay (IHA). The overall seroprevalence of chlamydial infection in dairy cattle was 7.25% (29/400). Greater than or equal to eight-yr-old dairy cattle had the highest seroprevalence (10.34%), followed by those that were ≥ 6 years old or < 7 years old dairy cattle (10.20%), although there were no statistically significant differences among different groups (P > 0.05). Dairy cattle with 5 pregnancies had the highest seroprevalence (10.81%). These results indicate that chlamydial infection was present in dairy cattle in Guangzhou, subtropical southern China, and integrated strategies and measures should be executed to control and prevent chlamydial infection and disease outbreak in the study region.     

Economic evaluation of the production impact of bovine schistosomiasis and vaccination in the Sudan

This study was done to evaluate the estimated economic consequences of the recent discovery that an irradiated Schistosoma bovis vaccine was effective in reducing mortality and intensity of infection in cattle after field exposure to S. bovis in the White Nile province. The benefits and costs were hypothesized to occur over a 5-year period starting after the vaccine had been further developed to optimal commercial usefulness.

The potential benefits of vaccination are from the avoidance of mortality and growth delay losses caused by S. bovis infection and were based on an owner survey conducted in 1981. These benefits were discounted from the time of their potential marketing opportunity to the first year of a vaccination program at 15% per annum and were valued on a basis of 1982 prices for live cattle exported to Egypt and Saudi Arabia. Variations in benefits stem from degree of infection probability, mortality and morbidity estimates and percent of animals vaccinated. Since clinical schistosomiasis (“gorag” — sunken-eyed appearance) and associated production losses occur almost exclusively in 6- to 30-month-old cattle, and there is evidence for long-term immunity, vaccinations would be given to cattle in this age-specific group or younger once in their lifetime. The principal variation in vaccination program costs, also valued at 1982 prices, is from vaccine production costs; $0.50 or $4.00 per dose. A vaccine efficacy of 70%, observed in a previously reported field trial, was used in these calculations.

Present value benefit—cost (b–c) ratios were estimated for the central, western and southern areas for high- and low-level effects of S. bovis impact on production and the vaccination program, cost and effectiveness. In an area (central provinces) of high infection probability (90%), high percentage of animals vaccinated (90%), high mortality (7.1%), and low vaccine production costs, the b–c ratio was 12.7. In contrast, a b–c ratio of 0.7 was estimated for an area (southern provinces) assuming low infection probability (50%), low percent of animals vaccinated (50%), lower mortality (3.55%) and high vaccine production costs. Potential returns from increased future milk and calf production and from faster herd build-up with younger females were not included in these benefit calculations. These results indicate that under most conditions further development of the vaccine and cost-effective vaccine production techniques would yield very favorable returns from improved livestock production efficiency in the Sudan. Export prices were assumed to not vary significantly with increased supply of export-quality cattle resulting from the estimated production losses avoided by vaccination against schistosomiasis.     

A serological survey of ruminant livestock in Kazakhstan during post-Soviet transitions in farming and disease control

The results of a serological survey of livestock in Kazakhstan, carried out in 1997--1998, are reported. Serum samples from 958 animals (cattle, sheep and goats) were tested for antibodies to foot and mouth disease (FMD), bluetongue (BT), epizootic haemorrhagic disease (EHD), rinderpest (RP) and peste des petits ruminants (PPR) viruses, and to Brucella spp. We also investigated the vaccination status of livestock and related this to changes in veterinary provision since independence in 1991. For the 2 diseases under official surveillance (FMD and brucellosis) our results were similar to official data, although we found significantly higher brucellosis levels in 2 districts and widespread ignorance about FMD vaccination status. The seroprevalence for BT virus was 23%, and seropositive animals were widespread suggesting endemicity, despite the disease not having being previously reported. We found a few seropositives for EHDV and PPRV, which may suggest that these diseases are also present in Kazakhstan. An hierarchical model showed that seroprevalence to FMD and BT viruses were clustered at the farm/village level, rather than at a larger spatial scale. This was unexpected for FMD, which is subject to vaccination policies which vary at the raion (county) level.     

Effectiveness of movement-prevention regulations to reduce the spread of foot-and-mouth disease in The Netherlands

After the foot-and-mouth disease (FMD) outbreak in 2001 the Dutch government implemented movement-prevention regulations to reduce the number of contacts between farms and consequently the risk of spread of highly contagious animal infections in the future. We studied the efficacy of these regulations by comparing registered cattle-movement data from 2000 to those from 2002. We also used the spatial and stochastic simulation model InterFMD to evaluate the consequences of the observed alterations in cattle-contact structure on the spread and control of a FMD epidemic.

There was a significant decrease in the number of cattle movements “for live use”, no difference in the number of group movements “for live use” and a distinct change in the overall contact structure. The most important structure changes were a decrease in the number of group movements from dairy farms to cattle-collection centres (−44%), and an increase in the number of group movements from dairy farms to beef farms (111%).

Our simulations demonstrated that the implemented regulations result in a concentration of the FMD-affected area and therefore in a reduction in size of the epidemics. Based on the intended Dutch strategy to control future FMD outbreaks, the decrease in extreme epidemics (95th percentiles) went from 31 infected farms in an epidemic-length of 65 days to 8 infected farms in an epidemic-length of 53 days in sparsely populated areas. In densely populated areas this decrease went from 135 infected farms to 103, while the duration reduced from 88 days to 81.     

Genetic variability of the resistance for three types of enteropathy in the growing rabbit

This paper describes the genetic variability for the resistance to three digestive stresses in the growing rabbit: after inoculation of coccidia (trial “coccidia”), with a fibre deficient diet (trial “FD”), and after experimental reproduction of epizootic rabbit enteropathy (trial “ERE”). Genetic variability was analysed from a sample of 48 sires, which produced the experimental young rabbits. These animals were examined on D0, D4, D11, D18, D25 and D32 after weaning (at 30 days old). Three clinical symptoms were checked: bloated abdomen, diarrhoea and mucus. Mortality and clinical symptoms were used to assess an individual response to each digestive stress. Two binary indexes were defined to describe this rabbit individual response. The first one (“Alive”) dealt with mortality. The second (“Tolerant”) dealt with mortality and morbidity. “Alive”, and “tolerant” percentages were low for the “coccidia” trial (61% and 23% respectively), high for the “FD” trial (75% and 36% respectively) and intermediate for the “ERE” trial (66% and 37% respectively). The sire effect was significant for each index in the “coccidia” and the “FD” trials. The sire effect was significant for the “tolerant” index in the “ERE” trial. Correlations between sire rankings for the two indexes of one trial were often significant. Correlations between sire rankings for indexes of “coccidia” and “FD” trials were weakly significant. Our results demonstrate that there is a genetic variability for the resistance to three different enteropathies.     

Risk factors for Marek's disease and mortality in white Leghorns in Norway

A prospective longitudinal field study was conducted in the period from January 1994 to January 1996 to analyse the relationship between some selected risk factors in the growing and laying periods and (1) the flock-level occurrence of Marek’s disease (MD) during the period from 16 to 32 weeks of age and (2) the cumulative mortality during the same period. A total of 171 layer flocks in 102 egg-production farms were included in the statistical analyses.

A logistic regression (with strain of layer and vaccination program against MD as fixed effects) of flock-level MD-status during the first 16 weeks of the laying period was conducted. Of the risk factors investigated, “multi-age management” and “housing system” were significantly associated at the rearing farm, and “number of hens in each cage” at the egg-production farm. Flocks kept in single-age facilities had a lower risk of MD than flocks housed in farms with multi-age management. The odds of MD were larger for flocks housed on a litter floor in the rearing farms compared to flocks housed in battery cages. At the egg-production stage, flocks kept in battery cages housing more than three hens were at greater risk of MD than those held in cages for three hens or less.

A weighted least-squares regression (with strain of layer and flock-level MD-status as fixed effects) of cumulative mortality during the period from 16 to 32 weeks of age was also run. The same risk factors (with the same directions of effects) and “size of the rearing farm” were included in the final model of mortality. Chicks reared in medium-sized farms were at higher risk of dying than those coming from either small or large rearing farms. Our results confirm the importance of preventing chicks from being exposed to MD-virus during the rearing period, to reduce the risk of MD-outbreaks (and thereby, mortality losses) during the early stage of the egg-laying period.     

Seroprevalence and potential risk of bovine brucellosis in zerograzing and pastoral dairy systems in Uganda

A cross-sectional study was conducted in Uganda between November 2006 and February 2007 to assess the seroprevalence and risk of brucellosis in zerograzing and pastoral dairy systems; two major sources of milk in Uganda, 80% of which is sold unpasteurized to consumers through informal channels. A total of 723 cattle comprised of 497 animals from the pastoral system and 226 animals from the zerograzing system were tested for antibodies against natural B. abortus infection using the competitive enzyme-linked immunosorbent assay (C-ELISA). Herd-level seroprevalence was 100% in the pastoral system and 5.5% (95% CI: 1.8, 9.2) in the zerograzing system. The animal-level seroprevalence and within-herd range of brucellosis in cattle in the pastoral system were 34.0% (95% CI: 29.9, 38.1) and 8.1–75.9%, while for those in the zerograzing system were 3.3% (95% CI: 0.9, 5.7) and 0–9.0%. Abortion rates of 23% and 0% among seropositive cows vis-à-vis 5.4% and 1.9% among seronegative cows were recorded in the pastoral and zerograzing systems, respectively. The risk of natural B. abortus infection was higher among older cattle (>24 m) (Odds ratio [OR] = 1.83, 95% CI: 1.25–2.67) and dry cows (OR = 2.01, 95% CI: 1.23–3.31) in the pastoral system, and in calves aged 0–6 m (OR = 5.72, 95% CI: 1.04–31.41) in the zerograzing system. Implementing a culling program in the zerograzing system to eliminate the existing low risk of brucellosis and targeting calves in the pastoral systems for vaccination could avert the cost-related limitation of brucellosis control in Uganda.     

Herd demographics correlated with the spatial distribution of a foot-and-mouth disease epidemic in Buenos Aires province, Argentina

During a recent foot-and-mouth disease epidemic in Argentina, cattle herds affected in 2001 were located mainly (69%) in Buenos Aires province. The densities of outbreaks (no. of outbreaks per km²) and cattle-demographic variables in the province were estimated using a geographical information system and kernel function. Before the epidemic officially was recognized, the density of outbreaks was correlated (r_sp = 0.28–0.47) with the geographic distribution of small (≤100 cattle), dairy and fattening herds. During the mass-vaccination campaign to control the epidemic (April–July), the density of outbreaks was most strongly correlated (r_sp = 0.20–0.25) with the distribution of large (>500 cattle) and breeding herds. After the end of the mass-vaccination campaign, large herds and number of cows were most strongly correlated (r_sp = 0.16–0.26) with outbreak density. These relationships might indicate that: (1) the disease spread more rapidly or was more easily detected in intensive production systems at the beginning of the epidemic; (2) vaccination and other control methods applied were less effective in large, semi-intensive production systems; (3) incomplete vaccine protection was responsible for herd outbreaks that occurred after the end of the mass-vaccination campaign.     

Prevalence of contagious bovine pleuropneumonia (CBPP) in northern Nigeria

An abattoir study on the prevalence of contagious bovine pleuropneumonia (CBPP) in five cattle-producing states of Nigeria from 1988 to 1997 was carried out. A total of 1,936,015 slaughtered cattle was examined for characteristic CBPP lung lesions. The overall lesion-based prevalence of CBPP was 0.29% (95% CI 0.24, 0.35). The prevalence varied significantly (P<0.05) by state but not across the years. A total of 279 CBPP outbreaks occurred and overall vaccination coverage was only 9.7%, both varied over the years and across the states. The reasons for inadequate vaccination coverage for CBPP as well as the need for re-establishment of a national CBPP control programme are suggested.     

Continuing presence of rinderpest virus as a threat in East Africa, 1983-1985

The re-emergence of rinderpest virus in East Africa in 1979 caused widespread outbreaks of disease and subclinical infection throughout the region until mid-1983. Subsequent massive emergency vaccination campaigns have been successful in eliminating clinical rinderpest from Tanzania and preventing its spread southwards. Unfortunately the virus is still endemic in north-eastern Uganda and has recently caused epidemic outbreaks with high mortality in cattle in that country. In Kenya, buffaloes (Syncerus caffer) in and around the Masai Mara game reserve have developed antibodies to rinderpest virus as recently as late 1984. Although there have been no outbreaks of clinical disease in Tanzania or Kenya from April 1983 to the end of 1985 this serological evidence plus the increasing incidence of clinical outbreaks in Uganda indicate that rinderpest virus still threatens East Africa. The substantial aid which has been provided to the region for rinderpest control must be maintained.     

Seroprevalence of Leptospira Hardjo in the Irish suckler cattle population

Background

Prior to the present study, the seroprevalence of leptospirosis in Irish suckler herds was unknown. In this study, we describe the herd and animal-level prevalence of Leptospira Hardjo infection in the Irish suckler cattle population. For the purposes of the study, the 26 counties of the Republic of Ireland were divided into 6 regions from which a representative number of herds were selected. A herd was considered eligible for sampling if it was not vaccinating against leptospirosis and if it contained ≥ 9 breeding animals of beef breed ≥ 12 months of age. In total, 288 randomly selected herds were eligible for inclusion in the seroprevalence dataset analysis. Serological testing was carried out using a commercially available monoclonal antibody-capture ELISA, (sensitivity 100%; specificity 86.67%).

Results

Herds were categorised as either “Free from Infection” or “Infected” using the epidemiological software tool, FreeCalc 2.0. Using this classification, 237 herds were “Infected” (82.29%). The South West and South East regions had the highest herd prevalence. The regional effect on herd prevalence was largely mirrored by breeding herd size. A true animal-level prevalence of 41.75% was calculated using the epidemiological software tool, TruePrev. There was a statistically significant regional trend, with true prevalence being highest in the South East (P < 0.05). The median Breeding Herd Size (BHS), when categorised into quartiles, had a statistically significant influence on individual animal true seroprevalence (P < 0.001); true seroprevalence increased with increasing BHS.

Conclusions

Leptospirosis is a widespread endemic disease in the Republic of Ireland. It is possible that economic losses due to leptospirosis in unvaccinated Irish suckler herds may be underestimated.     

Estimates of within-herd incidence rates of Mycobacterium bovis in Canadian cattle and cervids between 1985 and 1994

We analysed the individual-animal data from six of the nine outbreaks of tuberculosis in Canadian cattle and cervids from 1985 to 1994. A “positive/reactor” animal was one which had either a positive culture or a positive or suspicious reaction on a mid-cervical, comparative cervical, or gross or histopathological test for tuberculosis. Individual-animal data were collected only for herds which had one or more positive/reactor animals. Data were collected from the outbreak records in the Regional or District offices of Agriculture and Agri-food Canada’s Animal and Plant Health Directorate. The within-herd spread of Mycobacterium bovis was studied by determining the most-likely date at which the herd was first exposed to M. bovis and the number of reactions which had developed by the time the herd was investigated. The animal-time units at risk in the herd were probably overestimated, resulting in conservative estimates of the within-herd incidence rates. Negative-binomial regression was used to investigate factors which might have influenced the within-herd spread of tuberculosis. Increasing age appeared to be a risk factor for being a positive/reactor animal. When compared to animals 0–12 months old, animals 13–24 months old had an incidence rate ratio (IRR) of 7.6, while animals >24 months old had an IRR of 10.4 (p=0.009). Actual and predicted incidence rates for tuberculosis in mature (>24 months old) animals were calculated. Actual and predicted incidence rates were similar for cervids, within an outbreak. There was more variability between actual and predicted rates in the dairy and beef animals. In the one outbreak (Ontario) where there were positive/reactor cervid, dairy and beef herds, the actual incidence rate for cervids (IR=9.3 cases per 100 animal-years) was almost twice that of dairy cattle (IR=5.0) and three times that of beef cattle (IR=3.1).     

Brucellosis among smallholder cattle farmers in Zambia

A cross-sectional study was performed in Southern and Lusaka provinces of Zambia between March and September 2008 to estimate Brucella seroprevalence in cattle kept by smallholder dairy farmers (n = 185). Rose Bengal test (RBT) was used as a screening test followed by confirmation with competitive ELISA (c-ELISA). We investigated 1,323 cattle, of which 383 had a history of receiving vaccination against brucellosis and 36 had a history of abortion. Overall seroprevalence was 6.0% with areas where vaccination was practiced having low seroprevalence. Age was associated with Brucella seropositivity (P = 0.03) unlike cattle breed (P = 0.21) and sex (P = 0.32). At area level, there was a negative correlation (Corr. coeff = −0.74) between percentage of animals with brucellosis vaccination history (vaccination coverage) and level of brucellosis; percentage of animals with history of abortion (Corr. coeff. = −0.82) and brucellosis vaccination coverage. However, a positive correlation existed between brucellosis infection levels with percentage of animals having a history of abortion (Corr. coeff. = 0.72). History of vaccination against brucellosis was positively associated with a positive Brucella result on RBT (P = 0.004) whereby animals with history of vaccination against brucellosis were more likely to give a positive RBT test results (OR = 1.52). However, the results of c-ELISA were independent of history of Brucella vaccination (P = 0.149) but was positively associated with history of abortion (OR = 4.12). Our results indicate a relatively low Brucella seroprevalence in cattle from smallholder dairy farmers and that vaccination was effective in reducing cases of Brucella infections and Brucella-related abortions. Human exposure to Brucella through milk from smallholder farmers could result through milk traded on the informal market since that milk is not processed and there no quality and safety controls.