The status of bovine brucellosis in Ethiopia with special emphasis on exotic and cross bred cattle in dairy and breeding farms

Seroprevalence and potential risk factors of brucellosis in sheep from America, Africa and Asia regions: A systematic review and meta-analysis

BACKGROUND

Brucellosis, a neglected and global zoonotic disease, infect a variety of mammals, among which sheep are one of the main hosts. This disease results in huge economic losses and is a widespread concern around the world.

RESULT

Based on the selection criteria, 40 articles from 2010 to 2021 of five databases (CNKI, Wanfang, VIP, PubMed and Science Direct) reported in America, Africa and Asia were included. The data showed that during this period, the overall seroprevalence of sheep brucellosis on these three continents was 6.2%. At the regional level, sheep brucellosis had the highest seroprevalence (8.5%) in Africa and the lowest seroprevalence (1.9%) in the Americas. With regard to the age of the sheep, the seroprevalence was significantly higher in adult sheep (15.5%) than in lambs (8.6%). Further, the seroprevalence was significantly higher in sheep that had abortion (44.3%) than in pregnant (13.0%) and non-pregnant sheep (9.5%). With regard to herd size, herds with >20 sheep (35.4%) had a significantly higher seroprevalence than herds with <20 sheep (16.8%). In terms of farming and grazing mode, free-range rearing (8.4%) was associated with a significantly higher seroprevalence than intensive farming (2.8%), and mixed grazing (37.0%) was associated with a significantly higher seroprevalence than single grazing (5.7%).

CONCLUSION

Sheep brucellosis is widely distributed in sheep-rearing regions of America, Africa and Asia, and sheep are susceptible to brucellosis by themselves or from other infectious sources. Therefore, timely monitoring of ovine brucellosis and improving farming and grazing patterns are critical to reducing the prevalence of brucellosis.

Comparative evaluation of RBPT, I-ELISA, and CFT for the diagnosis of brucellosis and PCR detection of Brucella species from Ethiopian sheep, goats, and cattle sera

BACKGROUND

Brucellosis is an economically devastating animal disease and has public health concern. Serological methods such as Rose Bengal Plate Test (RBPT), Complement Fixation Test (CFT), and Indirect-Enzyme-Linked Immunosorbent Assay (I-ELISA) have been used to detect brucellosis. However, there is limited comparative evaluation studies and lack of molecular confirmation of the causative agents in the study areas. The study was aimed to compare RBPT, I-ELISA, CFT, and confirmation using Polymerase Chain Reaction (PCR). A total of 2317 sera samples were collected from brucellosis-affected areas of Ethiopia with no vaccination history. All sera were subjected to comparative serological assays. Post-cross tabulation, sensitivity, and specificity were determined using Receiver Operating Characteristics (ROC) curve analysis software. PCR was performed on 54 seropositive samples using genus- and species-specific primers.

RESULTS

Among the 2317 sera tested for comparative serological assays, 189 (8.16%) were positive for RBPT, 191 (8.24%) for I-ELISA, and 48 (2.07%) for CFT. Sensitivity to RBPT was 100% (95%) in shoats and 74% (95%) in cattle. Specificity on RBPT was 98.69% (95%), 99.28% (95%), 100% (95%) in sheep, goats, and cattle, respectively. CFT sensitivity was 4 (95%) in sheep, 9.65 (95%) goats, and 72 (95%) cattle. Specificity on CFT was 100% (95%) for sheep, goats, and cattle. A 223bp Brucella genus-specific and 156bp B. abortus species-specific detected. However, B. melitensis not detected.

CONCLUSION

In this study, I-ELISA was the most sensitive and specific test. RBPT detected all Brucellosis-infected sheep and goats; nevertheless, it showed false positive in sheep and goats and false negative in cattle. The presence of B. abortus in small and large ruminants was confirmed by PCR. This is the first report of B. abortus detection in small ruminant in Ethiopia. B.abortus detected in non-preferred hosts. The findings suggest further study on molecular epidemiology of Brucella species.

Herd and animal level seroprevalence and associated risk factors of bovine brucellosis in different agro-ecologies of southwest Ethiopia

Brucellosis is a zoonotic infection that commonly affects cattle in Ethiopia, causing significant negative economic impact. A cross-sectional study was carried out between November 2020 and November 2021 in southwest Ethiopia to determine the seroprevalence of brucellosis and its associated risk factors in cattle herds. Blood samples were taken from 461 randomly selected cattle to test for the presence of Brucella antibodies using the Rose Bengal Plate test, with positive serum confirmed through the complement fixation test. A multivariable random effect logistic regression analysis was used to identify potential risk factors for Brucella seropositivity. The study found 7.14% (95% CI: 4.44-9.01) seroprevalence at the animal level and 12.23% (95% CI: 6.52-16.05) at the herd level based on the complement fixation test. Age (OR = 6.9, 95%CI: 1.83-15.97), herd size (OR = 3.66, 95%CI: 1.39-9.61), introducing new animals (OR = 2.72, 95%CI: 1.17-6.29), management system (OR = 12.2, 95%CI: 1.53-26.80), species composition (OR = 4.24, 95%CI: 1.51-11.91), and abortion (OR = 7.1, 95%CI: 1.93-15.39) were found to be associated with Brucella seropositivity. The analysis also revealed two risk factors for Brucella infection at the herd level, including herd size (OR = 3.4, 95% CI: 1.05-10.68) and species composition (OR = 3.1, 95% CI: 1.20-7.88). The presence of Brucella antibodies in cattle highlights the need for increased awareness and measures to mitigate the identified risk factors of the disease to prevent its spread. Furthermore, further studies are necessary to investigate the zoonotic transmission of brucellosis to humans and its role in cattle reproduction disorders in the study area.

Seroprevalence of Bovine Brucellosis in Selected Sites of Central Highland of Ethiopia

Background

Brucellosis is a contagious, economically significant bacterial disease that affects animals worldwide and is one of the most neglected zoonotic diseases in the world. The disease poses a barrier to the trade of animals and animal products, represents a public health hazard, and is an impediment to free animal movement.

Methods

A cross-sectional study was carried out from December 2019 to May 2020 in order to determine seroprevalence and identify potential risk factors for brucellosis in dairy cows in the Central Highlands of Ethiopia with recent cases of abortion. Purposive sampling was carried out on the farms and kebeles in question to screen for recent cases of abortion in dairy cows. For the purpose of performing serological testing, 352 blood samples from dairy cattle were obtained. The Rose Bengal Plate test was used to initially screen the serum samples, and the Complement Fixation test was utilized as a confirmatory test.

Results

Using combined RBPT and CFT tests, the overall seroprevalence of bovine brucellosis was 0.6% (95% CI: 0.16-2.09). Retained fetal membrane (OR = 32.74, p = 0.006), market-based stock replacement (OR = 16.55, p = 0.002), breeding method (OR = 7.58, p = 0.027), and late stage of abortion (OR = 14.74, p = 0.0002) are all significantly associated risk factors.

Conclusion

The present seroprevalence study revealed that brucellosis is prevalent at a lower rate among dairy cattle in the study areas. However, there is a possible risk of brucellosis transmission in dairy cattle and the exposed human population in research locations because no control measures were put in place there. Implementing a test and slaughter method with compensation for farmers is advised due to the low prevalence of bovine brucellosis in government-owned and small-holder farms.

The Status and Risk Factors of Brucellosis in Smallholder Dairy Cattle in Selected Regions of Tanzania

Bovine brucellosis is a bacterial zoonoses caused by Brucella abortus. We conducted a cross-sectional study to determine brucellosis seroprevalence and risk factors among smallholder dairy cattle across six regions in Tanzania. We sampled 2048 dairy cattle on 1374 farms between July 2019 and October 2020. Sera were tested for the presence of anti-Brucella antibodies using a competitive enzyme-linked immunosorbent assay. Seroprevalence was calculated at different administrative scales, and spatial tests were used to detect disease hotspots. A generalized mixed-effects regression model was built to explore the relationships among Brucella serostatus, animals, and farm management factors. Seroprevalence was 2.39% (49/2048 cattle, 95% CI 1.7-3.1) across the study area and the Njombe Region represented the highest percentage with 15.5% (95% CI 11.0-22.0). Moreover, hotspots were detected in the Njombe and Kilimanjaro Regions. Mixed-effects models showed that having goats (OR 3.02, 95% C 1.22-7.46) and abortion history (OR 4.91, 95% CI 1.43-16.9) were significant risk factors for brucellosis. Education of dairy farmers regarding the clinical signs, transmission routes, and control measures for brucellosis is advised. A One Health approach is required to study the role of small ruminants in cattle brucellosis and the status of brucellosis in dairy farmers in the Njombe and Kilimanjaro Regions.

Detection of Antibodies Against Brucellosis and Associated Risk Factors in Cross Breed Dairy Cattle in Smallholder Farmers, Southern Ethiopia

Background

A cross-sectional study was conducted in selected districts of Gamo zone, southern Ethiopia over a period of November 2019 and September 2020 to estimate seroprevalence and associated risk factors and assess knowledge and practices of smallholder farmers about bovine brucellosis. Two districts and four kebeles from each district were purposively selected, and individual animals were sampled using a simple random sampling technique. A total of 384 sera samples were collected, and concurrently, 236 dairy cattle owners were interviewed. The samples were tested for antibodies against Brucella using both Rose Bengal Plate test and Complement Fixation test following OIE standard protocol. Risk factors associated with bovine brucellosis were analyzed using univariate and multivariate logistic regressions.

Results

The survey result has shown that 95% and 97% of the small holder farmers did not know the cause and symptoms of bovine brucellosis, respectively, and the majority have engaged in risky practices. Eight (2.08%) of the collected serum samples were positive with screening test (RBT) and only six (1.5%) were positive with confirmatory test (CFT). Multivariable logistic regression analysis showed a statistically significant association between herd sizes and the disease. The seropositivity of the disease is higher in small-sized herds followed by medium-sized herds.

Conclusion

The seroprevalence of bovine brucellosis was found to be at a low percentage with confirmatory tests even if there was a presence of associated risk factors for the disease in the study area. Again, the results suggest that smallholder farmers have poor knowledge and risky practices, which expose them to the disease. Awareness creation about the disease is of paramount importance even if the prevalence was low in this serological study. The implementation of a test and slaughter program before the disease becomes widespread, along with the testing of new stock before introduction to the farms is recommended.

Seroepidemiology of selected transboundary animal diseases in goats in Zambia

Transboundary pathogens of goats present significant constraints to the livelihoods of millions of farmers in countries such as Zambia. Consequently, this study aimed to investigate the seroprevalence of Mycoplasma capricolum subsp. capripneumoniae (Mccp), foot and mouth disease virus (FMDV), Brucella spp., Crimean Congo haemorrhagic fever virus (CCHFV), and Rift Valley fever virus (RVFV) in Zambian goats. Another aim was to identify associations between seroprevalence and different predictor variables, such as trade and border proximity. From September to October 2019, 962 serum samples were collected from goats in seven Zambian districts, four of which have an international border while the remaining three do not. A questionnaire survey was conducted with each household, focusing on trade routines, management strategies and herd disease history. Animal-level seroprevalence adjusted for herd-level clustering was 8.2 % (95 % confidence interval [CI] 7.5-9.0) for Mccp, 12.9% (95% CI 12.0-13.7) for FMDV, 13.0 % (95% CI 12.1-13.9) for Brucella spp., 3.3 % (95% CI 2.8-3.7) for CCHFV, and 0.4 % (95 % CI 0.3-0.7) for RVFV. The association between herd-level seroprevalence and border proximity and trade appeared negligible, with the exception of selling goats at least twice a year which was identified as a potential risk factor for Brucella spp. (OR 4.1, 95 % CI 1.1-16.0, p = 0.040). In addition, a positive association between herd-level seroprevalence of FMDV and a herd size of 21 goats or more (OR 3.3, 95 % CI 1.0-11.1, p = 0.049) was detected. Also, positive associations between animal-level seroprevalence of Brucella spp. and increasing age (OR 7.7, 95 % CI 1.5-40.7, p = 0.016), and CCHFV and keeping pigs in the household (OR 2.7, 95 % CI 1.0-7.1, p = 0.044), were found. For FMDV (OR 3.8, 95 % CI 1.4-10.9, p = 0.011) and Brucella spp. (OR 4.5, 95 % CI 1.2-17.3, p = 0.031) on the other hand, animal-level seroprevalence was significantly higher in households without pigs. To the best of the authors' knowledge, this is the first study to describe the presence of antibodies for CCPP and CCHF in the Zambian goat population. While the association between seroprevalence and trade and border proximity generally appeared negligible, it is recommended that their influence is further evaluated in future studies, preferably through in-depth longitudinal studies incorporating impacts of different biosecurity measures and trade variations, linked to for example seasonality and trade peaks.

Cross-Sectional Study of Seroprevalence and Associated Risk Factors of Bovine Brucellosis in Selected Districts of Jimma Zone, South Western Oromia, Ethiopia

Bovine brucellosis is one of the most widespread but neglected zoonotic diseases in developing countries where it is an endemic and growing problem causing public health impacts. Developing a cost-effective control strategy of the disease can only be guaranteed by knowledge of the disease epidemiology that defines its risk profiles. Hence, this study was designed to evaluate epidemiological aspects of bovine brucellosis in selected districts of Jimma zone. A cross-sectional study with multistage sampling techniques was conducted on 424 cattle to evaluate its seroprevalence. Likewise, 114 households were included for the investigation of risk factors. SPSS version 20 for data analysis and C-ELISA test for antibody detection were used. Moreover, the chi-square test for univariable analysis and logistic regression model for multivariable analysis were employed to assess association between seropositivity and risk factors. From this study, 3.3% (95% CI: 1.82-5.48) and 12.3% (95% CI: 6.88-19.75) seroprevalence of the disease was detected with the highest proportion found at Kersa district (6.5 (95% CI: 1.37-17.90) and (21.4 (95% CI: 4.66-50.80)) followed by Seka Chokorsa (1.76 (95% CI: 0.37-5.07) and (6.7 (95% CI: 1.40-18.27)) and Mana (1.75 (95% CI: 0.21-6.20) and (7.1 (95% CI: 0.88-23.50)) at individual animals and herd levels, respectively. Cattle of poor body condition, pregnant, and cows with history of abortion and repeat breeding were found 4.8 (95% CI: 2.00-22.74), 4.3 (95% CI: 1.43-13.04), 3.3 (95% CI: 1.07-10.21), and 2.7 (95% CI: 1.86-8.15) times more likely seropositive than their counterparts, respectively. Besides these, mixed feeding style was highly associated with seropositive reactors than separate feeding (AOR = 8.3; 95% CI: 1.76-38.99). These findings depicted substantial areas to be addressed in implementation of appropriate and immediate control actions and establishment of intervention mechanisms of bovine brucellosis.

Crossing the Line: Seroprevalence and Risk Factors for Transboundary Animal Diseases Along the Tanzania-Zambia Border

Transboundary pathogens pose a threat to livelihood security in countries such as Zambia and Tanzania. This study aimed to investigate the seroprevalence of peste des petits ruminants virus (PPRV), foot and mouth disease virus (FMDV), sheep and goat pox virus (SGPV), Rift Valley fever virus (RVFV) and Brucella spp. in sheep and goats along the Tanzania-Zambia border. Another aim was to assess the association between certain predictor variables and seroprevalence, focusing on trade and proximity to an international border, to a town and to the Tanzania-Zambia highway. During September-October 2018, 486 serum samples from small ruminants in Zambia and 491 in Tanzania were collected and analyzed using enzyme-linked immunosorbent assays (ELISA). A questionnaire focused on management strategies was administered to each household. The animal-level seroprevalence in Zambia was 0.21% [95% confidence interval (CI) (0.01–1.14) for PPRV, 1.03% (95% CI 0.33–2.39) for FMDV, 0% (95% CI 0–0.76) for SGPV, 2.26% (95% CI 1.14–4.01) for RVFV and 1.65% (95% CI 0.71–3.22) for Brucella spp.]. In Tanzania, animal-level seroprevalence was 2.85% (95% CI 1.57–4.74) for PPRV, 16.9% (95% CI 13.7–20.5) for FMDV, 0.20% (95% CI 0.01–1.13) for SGPV, 3.26% (95% CI 1.87–5.24) for RVFV and 20.0% (95% CI 14.5–26.5) for Brucella spp. For PPRV (OR 6.83, 95% CI 1.37–34.0, p = 0.019) and FMDV (OR 5.68, 95% CI 1.58–20.3, p = 0.008), herds situated more than 30 km from an international border were more likely to be seropositive, while being located 10–30 km (OR 4.43, 95% CI 1.22–16.1 p = 0.024) from a border was identified as a risk factor for Brucella spp. For FMDV (OR 79.2, 95% CI 4.52–1388.9, p = 0.003), being situated within 30 km from a town was associated with seropositivity. Furthermore, contact with wild ruminants (OR 18.2, 95% CI 1.36–244), and the presence of sheep in the household (OR 5.20, 95% CI 1.00–26.9, p = 0.049), was associated with seropositivity for PPRV, and FMDV. No significant associations between trade or distance to the Tan-Zam highway and seroprevalence were found. We recommend that the impact of trade and proximity to borders, towns and roads should be further evaluated in larger studies, ideally incorporating aspects such as temporal trade fluctuations.

Brucellosis in Ethiopia: A comprehensive review of literature from the year 2000-2020 and the way forward

Brucellosis is a zoonotic disease of considerable economic and public health significance globally. Despite the limited bacteriological evidence, a large number of serological works revealed that it is prevalent both in livestock and humans in Ethiopia. The current comprehensive review was carried out to provide apparent pooled seroprevalence (APS) estimates at individual animal and herd levels in livestock, and identify factors causing variability between studies conducted over the last two decades, show the spatial distribution, as well as summarizes Brucella species reported from livestock. It also provides APS of brucellosis in humans and evaluates the public health awareness of zoonotic brucellosis. In this review, systematic and synthetic review approaches were followed to summarize the available information. For the systematic review and meta-analysis, articles were selected based on predefined criteria. Data extracted from these articles were analyzed using meta-analytical approaches to provide APS estimates and in-between study variations for humans and all livestock species considered. Sensitivity analyses and bias assessments were conducted using influence plot analysis and, Egger's and Begg's statistics along with funnel plots, respectively. Synthetic review approaches were used to summarize data on isolates and public health awareness. Pooled seroprevalence estimate of brucellosis at national level was 2.6% (95% CI, 2.2-3.0) in cattle, 4% (95% CI, 3.1-5.1) in goats, 3% (95% CI, 2.3-3.9) in sheep and 3% (95% CI, 2.4-3.7) in camels. At a herd level, 16.3% (95% CI, 12.9, 20.5) of cattle, 12.1% (7.1, 19.9) of goat, 13.3% (7.6, 22.1) of sheep and 19.7% (13.8, 27.4) of camel herds in the country had at least one seropositive animal. Cattle in the pastoral/agropastoral production systems had significantly higher (p < 0.05) APS compared to mixed crop-livestock and urban/peri-urban dairy production systems. Pooled seroprevalence of brucellosis in small ruminants (8.3%, 95% CI, 6.3, 10.8) and camels (4.4%, 95% CI, 3.5, 5.6) in Afar were significantly higher (p<0.05) than in other regions. Reports conducted using ELISA and serial Rose Bengal plate test (RBPT)-ELISA had higher (p<0.05) APS estimates than serial RBPT and complement fixation test. Brucella melitensis and B. abortus were reported from goats and cattle, respectively, from three available reports. The APS of brucellosis in humans was 5% (95% CI: 3.3, 7.3). Public awareness of brucellosis was low (18.4%), while, practices that expose humans to Brucella infection were high. Scenario-based control interventions on regions and production systems using one health approach are suggested. This article is protected by copyright. All rights reserved.

Seroprevalence of Bovine Brucellosis and Associated Risk Factors in Western Ethiopia

Background

Brucellosis is a contagious bacterial disease, which affects domestic animals, humans, and wildlife in Ethiopia and other countries.

Methods

A cross-sectional study design using a simple random sampling technique was conducted in Diga, Guto, Gida, and Sibu Sire districts of East Wollega Zone, Western Oromia, from November 2019 to July 2020 to determine the prevalence of bovine brucellosis and identify associated risk factors. A lottery method was used during serum collection and risk factors identified during interview.

Results

A total of 1152 serum samples were collected from cattle of 6 months age and above. Serum samples were tested by enzyme linked immunosorbent assay (I-ELISA). An overall seroprevalence of brucellosis was 1.82% (21/1152). Statically significant variation (P<0.05) in seroprevalence of bovine brucellosis was recorded among potential risk factors such as breed [P≤0.05; OR:8.905; CI:1.568–50.573], parity [P≤0.05; OR:0.017; CI:0.042–5.195], retained fetal membrane [P≤0.001; OR:0.018; CI:0.00–2.169], and abortion history [P≤0.001; OR:0.030; CI:0.004–0.212]. Conversely, seroprevalence variations in sex, district, villages, body condition score, and age were statistically insignificant (P>0.05).

Conclusion

The current study revealed bovine brucellosis is posing a threat to livestock with no strict control and prevention scheme in place. Therefore, public awareness creation about the zoonotic importance of the disease is crucial and the Government should establish legislation, support, control, and prevention of the disease recommended.

Seroprevalence of Bovine Brucellosis in Ethiopia: Systematic Review and Meta-Analysis

Brucellosis is an infectious and widespread zoonotic disease caused by bacteria of the genus Brucella and can induce considerable human suffering and huge economic losses in animals. Thus, the aim of this study was to conduct a systematic review and meta-analysis on the seroprevalence of bovine brucellosis in Ethiopia. PubMed, Science Direct, African Journals Online, and Google Scholar were used to search the articles. All references were screened and articles, which reported seroprevalence of bovine brucellosis in Ethiopia were included in the study. Meta-analysis using random-effects models was made to calculate the pooled seroprevalence of brucellosis. This review included 15 papers. The estimated pooled seroprevalence of brucellosis was found to be 3.0% (95% CI: 2.0, 4.0). The subgroup analysis showed that there was a statistically significant association between the disease and geographical location, setting, laboratory technique employed and study years. Also, there was some evidence of publication bias (Egger's test, p = 0.0003) on studies reporting the prevalence of brucellosis in Ethiopia. This review proves a high seroprevalence of brucellosis in the country and appropriate control strategies are recommended. Moreover, further study on the risk factors is also required to develop cost-effective preventive strategies.

Sero-prevalence and associated risk factors of bovine brucellosis in Sendafa, Oromia Special Zone surrounding Addis Ababa, Ethiopia

Bovine brucellosis is an infectious bacterial disease caused by members of genus Brucella, affecting both animals and humans, and resulting in a serious economic loss in animal production sector and deterioration of public health. A cross-sectional study was conducted from November 2014 to April 2015 to determine the seroprevalence and associated risk factors of bovine brucellosis in Sendafa, Oromia Special Zone, Ethiopia. A total of 503 blood samples were collected using a simple random sampling technique from dairy cattle of above 6 months of age with no history of previous vaccination against brucellosis. All sera samples were subjected to both Rose Bengal Plate Test for screening and Complement Fixation Test for confirmation. Accordingly, the overall seroprevalence of bovine brucellosis in the study area was 0.40%. The result showed that the seroprevalence of bovine brucellosis in the study area was not statistically significant with all proposed risk factors. No reactors were observed in male animals. The seroprevalence was observed in animals without previous history of abortion. Moreover, information was gathered on individual animal and farm-level risk factors and other farm characteristics using a questionnaire. Awareness among society was poor, so the positive animals can be a potential hazard to animals and humans in the study area. Therefore, public education should be done to improve the awareness of the community on bovine brucellosis and its public health impact with due consideration on the safe consumption of food of animal origin.

A retrospective sero-epidemiological survey of bovine brucellosis on commercial and communal farming systems in Namibia from 2004 to 2018

Cattle production is the major livestock production activity and the mainstay of Namibia's economy. Sustained beef exports are contingent on a sound sanitary environment where diseases such as brucellosis are under control. In this retrospective study, 49,718 bovine brucellosis testing results from 2004 to 2018 were analyzed to determine the proportion of sero-positive cattle and herds, and the spatial distribution of positive reactors from commercial and communal areas. In total, 244 positive reactors were identified based on the Rose Bengal Test (RBT) and the Complement Fixation Test (CFT) in series, giving an overall proportion of infected animals of 0.49% (244/49,718; 95% CI, 0.43-0.56%) and an overall proportion of infected herds of 9.26% (78/842; 95% CI, 7.49-11.41%). There was a higher proportion of sero-positive communal herds (33.09%) and cattle (10.27%) than commercial herds (4.67%) and cattle (0.24%; p < 0.05). Annually, the proportion of positive reactors was 0-1.37% in the commercial area and 0-52.38% in the communal areas, with a clear decline in positive reactors in the communal areas. Within the commercial sector, the proportion of positive reactor dairy, beef, and export cattle was 0.19% (51/27,067; 95% CI, 0.14-0.25%), 0.30% (48/16,098; 95% CI, 0.22-0.40%), and 0.33% (16/4811; 95% CI, 0.20-0.54%), respectively. Abortions were found to be the major reason for Brucella testing in the communal areas. About 12.65% (96/759) of abortion-linked sera tested positive in the communal areas, but none were positive in beef or dairy cattle. Widespread vaccination of cattle and robust planned surveillance is recommended to reduce the incidence of the disease, its associated production losses and public health risk.

Zoonotic pathogens in urban animals: Enough research to protect the health of the urban population?

With more than half of the global population living in cities, the urban areas are also teeming with animals, including peridomestic wildlife, pets, and livestock. Urban animals may carry zoonotic pathogens, and crowded conditions in cities can increase the risk for the human population. We used a systematic approach to screen two publication databases as well as gray literature, and quantified the studies conducted on zoonoses in urban animals with respect to the geographic distribution, the host animal and pathogens. Out of 876 references found, 93 were included into final data extraction. Few studies were from the rapidly expanding cities in low- and middle-income countries where urban livestock-keeping is far more prominent than in high-income countries. Most studies were performed in peridomestic wildlife and pets, less in livestock. The most common category of pathogens studied were gastrointestinal parasites followed by gastrointestinal bacteria, whereas studies on some other zoonoses internationally recognized as critical for public health were few or absent. In conclusion, to mitigate the risks of emergence of zoonoses from urban animals this review highlights the research gaps on zoonoses, particularly in livestock in rapidly growing tropical cities and a more comprehensive inclusion of pathogens prioritized by WHO and OIE.

Brucellosis in the Addis Ababa dairy cattle: the myths and the realities

Background

Bovine brucellosis is considered as an important disease among livestock and people in sub-Saharan African countries including Ethiopia. A cross-sectional study was conducted from November 2016 to May 2017 to estimate the prevalence and associated risk factors, and to assess knowledge-attitude and practices (KAP) of farm workers about bovine brucellosis in Addis Ababa dairy farms.

Results

A total of 1550 cattle from 127 dairy farms were serially tested using the Rose Bengal Plate Test (RBPT), Competitive Enzyme-Linked Immunosorbant Assay (c-ELISA) and Complement Fixation Test (CFT). Forty-three (2.77%) of the collected sera were positive by the RBPT and only one of these was positive by c-ELISA (0.06%) and none was positive by CFT. The knowledge of farm workers towards the disease was very low and risk factors associated with Brucella infection were apparent in the study area.

Conclusion

Seropositivity for Brucella spp. was found in only a very small percentage by c-ELISA test, although risk factors for transmitting Brucella infection were present. The results suggest that bovine brucellosis is currently not a generalized problem in dairy cattle of Addis Ababa. Since this favorable disease situation is not the result of informed policy, there is no guarantee that it will continue unchanged. Setting clear policy in control of the disease and implementing “One Health” are the most constructive approaches recommended.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1709-4) contains supplementary material, which is available to authorized users.

Serosurvey for Infectious Agents Associated with Subfertility and Abortion in Dairy Cattle in Trinidad and Tobago, West Indies

Despite frequent reports of subfertility and abortion in dairy cattle in Trinidad and Tobago (T&amp;T), little is known about the potential infectious and non-infectious causes. This study set out to investigate possible infectious causes of reproductive problems by measuring the seroprevalence of four of the most significant reproductive pathogens in dairy cattle worldwide: Brucella abortus (B. abortus); Neospora caninum (N. caninum), Bovine Viral Diarrhoea virus (BVDV), and Infectious Bovine Rhinotracheitis virus (IBRV). These four reproductive pathogens have been suspected to be present in dairy cattle in T&amp;T for some time but, previously, studies have not been carried out to confirm their presence. Bulk milk samples were collected from 92 dairy farms across Trinidad, representing a total of 1177 dairy cattle. Four dairy farms were selected for individual milk sampling to assess in-farm seroprevalence levels. Milk samples were tested for antibodies to the four pathogens by commercial ELISA kits. The overall farm seroprevalence was 62% for N. caninium and 23% for IBRV, and no antibodies were detected in any of the bulk milk samples for B. abortus or BVDV. Mixed infections for IBRV and N. caninum were common. Seroprevalence levels were between 8% and 65% for N. caninum and between 3% and 53% IBRV on the four individual farms. These results reveal the presence of IBRV and N. caninum for the first time on the island of Trinidad and importantly reveal no evidence for the circulation of BVDV or B. abortus in dairy cattle in Trinidad.

Bovine herpesvirus-1 in three major milk sheds of Ethiopia: Serostatus and association with reproductive disorders in dairy cattle

Bovine herpesvirus-1 (BHV-1) causes infectious bovine rhinotracheitis (IBR), and infectious pustular vulvovaginitis (IPV) in cows and infectious pustular balanopostitis (IPB) in bulls worldwide. Infection of seronegative cattle with BHV-1 leads to abortion, retention of fetal membranes, increased service per conception, metritis and oophoritis. As part of an ongoing study on infectious causes of reproductive disorders in Ethiopia, this investigation aims at assessing the role of BHV-1 in the disorders and the risk factors affecting its seroprevalence. A cross-sectional study was conducted on a total of 1379 randomly selected dairy cattle from 149 herds. These dairy cattle were sampled from milks sheds of central (n = 555), western (n = 195) and southern (n = 629) Ethiopia. Blocking enzyme-linked immunosorbent assay (B-ELISA) was applied to detect antibodies specific to BHV-1. Additionally, a semi-structured questionnaire was administered and farm records were assessed to capture potential risk factors associated with BHV-1 seropositivity. Univariable and multivariable random-effects logistic regression analyses were used to assess potential risk factors associated with BHV-1 serostatus. Model fitness and reliability were assessed using the Hosmer and Lemeshow method and the receiver operating curve (ROC) respectively. An overall herd level BHV-1 seroprevalence of 81.8% (95% confidence interval (CI): 74.7-87.7%) and individual animal level seroprevalence of 41.0% (95% CI: 38.4-43.7%) were found. In a random-effects multivariable logistic regression model, the seroprevalence of BHV-1 exposure was higher in dairy cattle from breeding (Odds ratio [OR] = 1.3; p = 0.036) than in commercial (OR = 0.9; p = 0.137) and small-holder farms. Geographically, the prevalence was higher in western (OR = 1.4; p < 0.001) and southern Ethiopia (OR = 1.2; p < 0.001) than in central regions. BHV-1 seropositive cows had higher (p < 0.05) odds of clinical reproductive disorders including abortion, retained fetal membranes, stillbirth, birth of weak calf and metritis compared to seronegative cows. Thus, it is suggested that BHV-1 should be considered as differential diagnosis among improved dairy cattle herds with reproductive disorders in Ethiopia.

Serological prevalence and public health significance of brucellosis on a dairy farm in Namibia from 2011 to 2014

OBJECTIVE

The main objective of this study was to determine the serological prevalence of brucellosis on a dairy farm with no past history of abortions, but where Brucella control measures including test and slaughter and vaccination of heifers at 4-8 months of age was practiced. Secondary data from 2011 to 2014 obtained from the Epidemiology Section of the Directorate of Veterinary Services was used.

RESULTS

Mandatory annual brucellosis testing results for mature dairy cows on a dairy farm for the period 2011-2014 were collated and analyzed. Results of a total of 6912 cows were analysed. The data comprised of the year of testing, number of cows tested for Brucella antibodies and the number of cows that tested positive. Serological testing was carried out using the Rose Bengal Test (RBT) as a screening test and the Complement Fixation Test as a confirmatory test for results that tested positive on the RBPT. Over the 4-year period, one dairy cow tested positive for Brucella antibodies in 2013 giving an apparent prevalence of 0.05% and an overall prevalence of 0.01%. When apparent prevalence was adjusted for RBPT test specificity and sensitivity of 71 and 78% respectively, true prevalence was determined to be zero.

Characterisation of adopters and non-adopters of dairy technologies in Ethiopia and Kenya

While there is a general consensus that using dairy technologies, such as improved breeds of dairy cows, can substantially increase farm productivity and income, adoption of such technologies has been generally low in developing countries. The underlying reasons for non-adoption of beneficial technologies in the dairy sector are not fully understood. In this study, we characterised adopters and non-adopters of dairy technologies in Ethiopia and Kenya based on farmers' resources ownership in order to identify why many farmers in Ethiopia and Kenya have not adopted improved dairy technologies. As compared to non-adopters, farmers who adopt dairy technology own relatively more farm resources. The result signals that differences in resource endowments could lead to divergent technology adoption scenarios. Results show that a higher proportion of sample smallholders in Kenya have adopted dairy technologies than those in Ethiopia. Except for the use of veterinary services, fewer than 10% of sample farmers in Ethiopia have adopted dairy technologies-less than half the number of adopters in Kenya. The higher level of dairy technology adoption in Kenya can be ascribed partly to the long history of dairy development, including improvements in the value chain for the delivery of inputs, services and fluid milk marketing. Interventions that deal with the constraints related to access to farm resources and input and output markets could facilitate uptake of dairy technology in developing countries.

Brucellosis and associated risk factors in dairy cattle of eastern Ethiopia

Knowing the status of Bovine brucellosis and associated risk factors is a crucial step in formulating evidence based control scheme. In this study, a total of 967 dairy cows from 307 dairy farms in eastern Ethiopia were serologically tested for Brucella antibodies. The screening was done first using RBPT and positive samples were subsequently subjected to CFT for confirmation. A pre-tested structured questionnaire was used to collect relevant data from 307 dairy cattle owners or attendants to assess their awareness and routine practice. The data were run using univariable logistic regression analysis using STATA version 11.0 for Windows. Accordingly, herd and individual animal seroprevalence were found to be 6.8% (95% CI = 4.28-10.28) and 1.3% (95% CI = 0.72-2.29), respectively. The prevalence of sero-reactors among local breeds was observed to be higher compared to cross breed (p < 0.05). Herd level analysis of the risk factors indicated that in farms with large herd size (>20 animals), the odds ratio (OR) = 9.13, p = 0.00, CI = 3.01-27.69 of having brucellosis was 9.13 times higher than smaller size herds (<20 animals). Intensively managed herds had shown the highest seroprevalence (20.8%) than extensive (6.7%) and semi-intensive (4.2%). Experience of dairy handlers about the disease that cause abortion in late pregnancy was significantly associated (p < 0.001) with the occurrence of brucellosis in the herds. However, about 91% of the dairy cattle owners/attendants lack awareness about disease(s) that causes abortion in late pregnancy. Similarly risk of having brucellosis in those herds experiencing abortion was 6.3 times higher (OR = 6.3, p < 0.001, CI = 2.50-15.92). This study identified some of the handling practices for aborted and retained fetal materials to be risky. Therefore, the study highlights the need of comprehensive brucellosis surveillance in animal and human and institutions of public education and on farm biosafety measures in shaping proper disease control scheme.

Seroepidemiology of Human Brucellosis Among Blood Donors in Southern Ethiopia: Calling Attention to a Neglected Zoonotic Disease

Human brucellosis is neglected in southern Ethiopia. Although traditional food processing practices and animal husbandry which increase the risk of brucellosis are common, it has not been properly studied yet. This study was conducted to determine the seroepidemiology of brucellosis among apparently healthy individuals in southern Ethiopia. In the study, blood samples were collected to screen for serum agglutinins reactive to stained antigen of Brucella abortus Standard tube titration was performed for reactive serum to determine the titer of the agglutinin. A structured questionnaire was used to collect data on possible risk factors for brucellosis. The seroprevalence of human brucellosis in this study was found to be 10.6% (95% confidence interval = 7.0, 14.0). Possession of domestic ruminant animals, contact with ruminant animals, and husbandry practices at home were associated with seropositivity. The higher seroprevalence of human brucellosis in the study area needs attention and additional confirmatory investigation.

Brucellosis in Sub-Saharan Africa: Current challenges for management, diagnosis and control

Brucellosis is a highly contagious zoonosis caused by bacteria of the genus Brucella and affecting domestic and wild mammals. In this paper, the bacteriological and serological evidence of brucellosis in Sub-Saharan Africa (SSA) and its epidemiological characteristics are discussed. The tools available for the diagnosis and treatment of human brucellosis and for the diagnosis and control of animal brucellosis and their applicability in the context of SSA are presented and gaps identified. These gaps concern mostly the need for simpler and more affordable antimicrobial treatments against human brucellosis, the development of a B. melitensis vaccine that could circumvent the drawbacks of the currently available Rev 1 vaccine, and the investigation of serological diagnostic tests for camel brucellosis and wildlife. Strategies for the implementation of animal vaccination are also discussed.

Brucellosis Seropositivity in Animals and Humans in Ethiopia: A Meta-analysis

BACKGROUND

The objectives of this study were to assess the heterogeneities of estimates and to estimate the seroprevalence of brucellosis in animals and humans in Ethiopia.

METHODS/PRINCIPAL FINDINGS

Data from 70 studies covering 75879 animals and 2223 humans were extracted. Rose Bengal Plate Test (RBPT) and Complement Fixation Test (CFT) in series were the most frequently used serological tests. A random effects model was used to calculate pooled prevalence estimates. The overall True Prevalence of brucellosis seropositivity in goats and sheep were estimated at 5.3% (95%CI = 3.5, 7.5) and 2.7% (95%CI = 1.8, 3.4), respectively, and 2.9% for each of camels and cattle. The prevalence was higher in post-pubertal than in pre-pubertal animals (OR = 3.1, 95% CI = 2.6, 3.7) and in the pastoral than in the mixed crop-livestock production system (OR = 2.8, 95%CI = 2.5, 3.2). The incidence rates of brucellosis in humans of pastoral and sedentary system origins were estimated at 160 and 28 per 100 000 person years, respectively.

CONCLUSIONS

The seroprevalence of brucellosis is higher in goats than in other species. Its occurrence is evocative of its importance in the country in general and in the pastoral system in particular. Public awareness creation could reduce the transmission of Brucella spp. from animals to humans and the potential of livestock vaccination as a means of control of brucellosis needs to be assessed.

Bayesian Estimation of Sensitivity and Specificity of Rose Bengal, Complement Fixation, and Indirect ELISA Tests for the Diagnosis of Bovine Brucellosis in Ethiopia

Test evaluation in the absence of a gold standard test was conducted for the diagnosis and screening of bovine brucellosis using three commercially available tests including RBPT, CFT, and I-ELISA in National Animal Health Diagnostic and Investigation Center (NAHDIC) Ethiopia. A total of 278 sera samples from five dairy herds were collected and tested. Each serum sample was subjected to the three tests and the results obtained were recorded and the test outcomes were cross-classified to estimate the sensitivity and specificity of the tests using Bayesian model. Prior information generated on the sensitivity and specificity of bovine brucellosis from published data was used in the model. The three test-one population Bayesian model was modified and applied using WinBug software with the assumption that the dairy herds have similar management system and unknown disease status. The Bayesian posterior estimate for sensitivity was 89.6 (95% PI: 79.9-95.8), 96.8 (95% PI: 92.3-99.1), and 94 (95% PI: 87.8-97.5) and for specificity was 84.5 (95% PI: 68-94.98), 96.3 (95% PI: 91.7-98.8), and 88.5 (95% PI: 81-93.8) for RBT, I-ELISA, and CFT, respectively. In this study I-ELISA was found with the best sensitivity and specificity estimates 96.8 (95% PI: 92.3-99.1) and 96.3 (95% PI: 91.7-98.8), compared to both CFT and RBPT.

Serological survey of bovine brucellosis in Fulani nomadic cattle breeds (Bos indicus) of North-central Nigeria: Potential risk factors and zoonotic implications

A cross sectional study was conducted to investigate seroprevalence and associated risk factors of bovine brucellosis in Fulani nomadic herds in the 3 agro-ecological zones of Niger State, North-central Nigeria between January and August 2013. A total of 672 cattle in 113 herds were screened for Brucella antibodies using Rose Bengal Plate Test (RBPT) and confirmed by Lateral flow Assay (LFA). Data on herd characteristics and zoonotic factors were collected using structured questionnaire administered on Fulani herd owners. Factors associated with Brucella infection were tested using Chi-square test and multivariable logistic model. The overall cattle-level seroprevalence was 1.9% (95% CI: 1.1-3.2) with highest in agro-zone C (3.2%). Herd-level seroprevalence was 9.7% (95% CI: 5.23-16.29) and highest in agro-zone C (13.5%). Sex and agro-ecological zones were significantly (P<0.006 and P<0.01, respectively) associated with Brucella abortus seropositivity. Herd composition, abortion in herd, exchange of bulls for mating, introduction of new cattle, and socio-cultural practices were significantly associated with brucellosis occurrence. Inhalation of droplets from milk of infected cows, and drinking raw milk were less likely [OR 0.27; 95% CI: 0.09-0.82 and OR 0.27; 95% CI: 0.08-0.99, respectively] not to predisposed to brucellosis in humans. Eating infected raw meat, and contact with infected placenta were more likely [OR 7.49; 95% CI: 2.06-28.32 and OR 5.74; 95% CI: 1.78-18.47, respectively] to be risks for the disease in humans. These results highlighted the important risk factors for bovine brucellosis in Fulani herds. Thus, brucellosis control programs which take these factors into consideration will be beneficial.

Meta-analysis of Brucella seroprevalence in dairy cattle of Ethiopia

This meta-analysis estimates a single-group summary (effect size) for seroprevalence of Brucella spp. exposure in dairy cattle of Ethiopia. It also attempts to identify study-level variables that could explain the variation in apparent seroprevalence. The literature search was restricted to studies published in English language from January 2000 to December 2013. A template was designed to retrieve the most biologically plausible and consistent variables from the articles. A total of 29 published papers containing 40 animal-level studies were used in the analyses. The single-group summary of Brucella seroprevalence in cattle was estimated to reach 3.3 % with 95 % confidence interval (CI) (2.6-4.2 %). Of all the variables considered, region was the only specific factor identified to explain about 20 % of between-study variation. Accordingly, the region-based meta-analysis forest plot revealed the highest prevalence in central Ethiopia followed by southern part. The lowest prevalence estimate was observed in the western part of the country. The visual inspection of the funnel plot demonstrated the presence of possible publication bias which might dictate shortage of studies with higher prevalences or variance inflation due to infectiousness of Brucella. In conclusion, the quantitative review showed the seroprevalence to be low but widely distributed. More importantly, the review underscores the need for isolation and characterization of the circulating Brucella spp. to capture the type of Brucella spp. involved and its distribution in cattle in Ethiopia.

Seroprevalence investigation of bovine brucellosis in Macenta and Yomou, Guinea

Brucellosis is one of the world's major zoonotic diseases associated with reproductive disorders and a potential infection of human. Brucellosis leads to serious economic losses due to late-term abortion, stillbirth, weak calves, and sterility. In Guinea, the data on brucellosis was only detected as far back as 10 years ago. The purpose of this study was to estimate the prevalence of bovine brucellosis in the provinces of Macenta and Yomou of Guinea. A structured questionnaire was used in the clinical study, and 345 cattle were clinically examined. Three hundred serum samples were initially subjected to the Rose Bengal test (RBT); the positive results of which were confirmed by the complement fixation test (CFT). The investigation indicated that farmers had little information on brucellosis. Hygroma, abortion, sterility, and placental retention were the observed symptoms. Of the 29 RBT-positive samples, 26 were confirmed by CFT. The prevalence of brucellosis in Macenta and Yomou was 12 and 5.33 %, respectively. In both provinces, the prevalence mean was 8.67 %. This study highlighted the immediate necessity to carry out a strengthened surveillance of human and animal brucellosis to obtain as many data as possible in order to establish strategies for prevention and management of brucellosis in Guinea.