Caprine brucellosis in Kenya

Characterization of Brucella spp. and other abortigenic pathogens from aborted tissues of cattle and goats in Rwanda

Background

Abortions cause tremendous economic losses in food‐producing animals and may lead to food insecurity.

Objectives

This study aimed to characterize Brucella spp. and other abortigenic pathogens from aborted tissues of cattle.

Methods

For cattle, aborted tissues (n = 19) were cultured, and Brucella spp. were detected using the genus‐specific 16S‐23S ribosomal DNA interspacer region (ITS) assay and speciated using Brucella abortus, Brucella melitensis, Brucella ovis, and Brucella suis (AMOS) and Bruce‐ladder PCR assays. Brucella negative samples were screened using the eight abortigenic pathogens PCR panel. Samples from an abortion outbreak that occurred within a goat tribe were included in this investigation. Sera of females (n = 8) and males (n = 2) were analyzed using the Rose Bengal Test (RBT) and indirect enzyme‐linked immunosorbent assay (i‐ELISA), while vaginal swabs (n = 3) and aborted tissues (n = 1) were cultured and characterized.

Results

The ITS‐PCR detected Brucella DNA in cultures from two aborted tissues of cattle (10.5%, [2/19]), which were identified as B. melitensis (n = 1), and B. abortus (n = 1) using AMOS and Bruce‐ladder PCR assays. Campylobacter fetus (n = 7) and Leptospira spp. (n = 4) including co‐infections (n = 2) of C. fetus and Leptospira spp. were identified from the Brucella negative samples of cattle. Goats (100.0%, 10/10) were brucellosis seropositive on RBT and i‐ELISA. Mixed infections caused by B. melitensis and B. abortus were isolated from the vaginal swabs (n = 3) and aborted tissues (n = 1).

Discussion and conclusions

This is the first identification of abortion‐associated pathogens in aborted cattle indicating the enormous financial losses and a threat to public health. It is therefore essential to include these identified pathogens in the surveillance scheme of veterinary and human services.

Molecular epidemiology of Brucella species in mixed livestock-human ecosystems in Kenya

Brucellosis, caused by several species of the genus Brucella, is a zoonotic disease that affects humans and animal species worldwide. Information on the Brucella species circulating in different hosts in Kenya is largely unknown, thus limiting the adoption of targeted control strategies. This study was conducted in multi-host livestock populations in Kenya to detect the circulating Brucella species and assess evidence of host-pathogen associations. Serum samples were collected from 228 cattle, 162 goats, 158 sheep, 49 camels, and 257 humans from Narok and Marsabit counties in Kenya. Information on age, location and history of abortion or retained placenta were obtained for sampled livestock. Data on age, gender and location of residence were also collected for human participants. All samples were tested using genus level real-time PCR assays with primers specific for IS711 and bcsp31 targets for the detection of Brucella. All genus positive samples (positive for both targets) were further tested with a speciation assay for AlkB and BMEI1162 targets, specific for B. abortus and B. melitensis, respectively. Samples with adequate quantities aggregating to 577 were also tested with the Rose Bengal Test (RBT). A total of 199 (33.3%) livestock and 99 (38.5%) human samples tested positive for genus Brucella. Animal Brucella PCR positive status was positively predicted by RBT positive results (OR = 8.3, 95% CI 4.0-17.1). Humans aged 21-40 years had higher odds (OR = 2.8, 95% CI 1.2-6.6) of being Brucella PCR positive compared to the other age categories. The data on detection of different Brucella species indicates that B. abortus was detected more often in cattle (OR = 2.3, 95% CI 1.1-4.6) and camels (OR = 2.9, 95% CI 1.3-6.3), while B. melitensis was detected more in sheep (OR = 3.6, 95% CI 2.0-6.7) and goats (OR = 1.7, 95% CI 1.0-3.1). Both B. abortus and B. melitensis DNA were detected in humans and in multiple livestock host species, suggesting cross-transmission of these species among the different hosts. The detection of these two zoonotic Brucella species in humans further underpins the importance of One Health prevention strategies that target multiple host species, especially in the multi-host livestock populations.

Poor performance of the rapid test for human brucellosis in health facilities in Kenya

Human brucellosis is considered to be an important but typically under-diagnosed cause of febrile illness in many low and middle-income countries. In Kenya, and throughout East Africa, laboratory diagnosis for the disease is based primarily on the febrile antigen Brucella agglutination test (FBAT), yet few studies of the diagnostic accuracy of this test exist. Assessment of the performance of the FBAT is essential for its appropriate clinical use, as well as for evaluating surveillance data reported by public health systems. To assess FBAT performance, we collected sera from people with symptoms compatible with brucellosis attending two health facilities in Busia County, Kenya. Sera were tested using the FBAT and results compared with those from the Rose Bengal Test (RBT), an assay with well-known performance characteristics. Positives on either test were confirmed using the classical serum agglutination test (SAT)-Coombs test combination and a rapid IgM/IgG lateral flow immunochromatography assay (LFA). A questionnaire focussing on known risk factors for exposure to Brucella spp. was also conducted, and relationships with FBAT positivity examined using logistic regression. Out of 825 recruited individuals, 162 (19.6%) were classified as positive using the FBAT. In contrast, only eight (1.0%) were positive using the RBT. Of the 162 FBAT positives, one (0.62%) had an atypical agglutination in SAT and three (1.9%) showed low Coombs titres. Out of 148 FBAT positive individuals tested using the LFA, five (3.4%) were IgM positive and none were IgG positive. Poor or no correlation was observed between FBAT results and most established risk factors for Brucella infection. We observed substantial disagreement between the FBAT and a number of well-known serological tests, with the majority of reactive FBAT results appearing to be false positives. Poor FBAT specificity, combined with a lack of confirmatory testing, strongly suggests overdiagnosis of brucellosis is common in this low prevalence setting. This is expected to have important economic impacts on affected patients subjected to the long and likely unnecessary courses of multiple antibiotics required for treatment of the disease.

Brucellosis is a debilitating disease of people caused by infection with one of a number of different Brucella species. In almost all cases, people acquire the infection through exposure to infected animals or contaminated animal products. Human brucellosis is well known for its wide range of symptoms, and is often clinically indistinguishable from other infectious diseases, such as malaria or typhoid. Diagnosing the disease therefore typically relies on laboratory tests. A wide range of tests are available, but little is known about the accuracy of the principal test used in Government health facilities in Kenya, the febrile Brucella agglutination test (FBAT). In this study, we identified people with symptoms compatible with brucellosis attending health centres in Kenya. By comparing results from the FBAT performed on samples collected from these individuals with the results from a range of well-established diagnostic tests, we were able to show that the FBAT produces large numbers of false positive results. We expect that this leads to a high levels of overdiagnosis of brucellosis in some parts of Kenya. Treatment of the disease involves multiple weeks of multiple antibiotics, and these incorrect diagnoses may have important and unnecessary negative impacts on affected patients.

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 in sub-Saharan Africa: epidemiology, control and impact

Brucellosis is an important disease among livestock and people in sub-Saharan Africa. In general, the incidence is the highest in pastoral production systems and decreases as herd size and size of landholding decreases. The prevalence of risk factors for infections are best understood for bovine brucellosis and to a lesser extent for ovine and caprine brucellosis. The occurrence and epidemiology of brucellosis in pigs is poorly understood. This species bias is also reflected in control activities. As with other public-sector animal health services, the surveillance and control of brucellosis in sub-Saharan Africa is rarely implemented outside southern Africa. Brucellosis is even more ignored in humans and most cases go undiagnosed and untreated, leading to considerable suffering for those affected. Decision-making to determine the importance of brucellosis control relative to other public concerns and what brucellosis control strategies should be applied is urgently required. A strategy for how brucellosis decision-making might be considered and applied in future is outlined.

Serological responses to brucellosis in HIV-seropositive patients

Serial sera from 2 patients infected with the human immunodeficiency virus (HIV) type 1 attending a clinic in Nairobi, Kenya, and with blood cultures yielding Brucella melitensis, were tested by enzyme-linked immunosorbent assay for their serological response (Brucella-specific immunoglobulin (Ig) M and IgG) to Brucella infection. Antibody responses were comparable to those of immunocompetent individuals, one patient showing serology typical of acute brucellosis, the other of chronic brucellosis. Sera from 100 other patients, 65 of whom were HIV-positive, attending the same clinic but whose routine microbiological cultures were negative for Brucella, were tested retrospectively for Brucella-specific antibody. Eight had Brucella-specific IgM and IgG, 6 had IgM only and 21 had IgG only, suggesting relatively high levels of exposure to Brucella in the study cohort. There was no association between Brucella antibody status and HIV status. Brucellosis is probably underdiagnosed in Kenya. Brucella serology may be helpful in the diagnosis of patients with non-specific symptoms in East Africa, regardless of HIV status.

Brucellosis of camels in Kuwait

This study investigated the presence of Brucella antibodies in serum and milk obtained from camels in Kuwait. Brucella strains were also isolated from the foetus using standard technique (Webridge Lab Techniques). Three serological tests for serum were adopted. These tests were Rose Bengal Plate Test (RBPT), the Serum Tube Agglutination Test (SAT) and the Complement Fixation Test (CFT). The RBPT was used for all sera samples, and both SAT and CET were used for the positive RBPT. Camels that showed a titer of 1:40 in SAT or 1:5 in CFT or greater were considered positive. Thirteen of the samples examined were found positive by CFT (at 1:5); by SAT, they showed a titer of 1:20. One serological test, the Milk Ring Test (MRT), was used for milk. Here 3 and 2 were considered positive reactors but 1+ was considered suspicious. We were unable to isolate the Brucella organism from Sedemine and Cream of milk, but we isolated them from Foetus Brucella abortus and it is confirmed by Webridge Laboratory, U.K. It is Brucella abortus (Biovar 1). The prevalence rate was 14.8% from serum by the CFT and RBPT methods and 10.8% by the SAT method. For milk, the prevalence rate was 8.0%. Two Brucella abortus were isolated from 5 foetuses.

Survey of brucellosis in goats and sheep in the Yemen Arab Republic: comparison of tests for Brucella melitensis infection in sheep

Sera from 538 Yemeni goats and 690 Yemeni sheep were screened for brucellosis by the Rose Bengal Plate Test (RBPT) and reactors confirmed by the complement fixation test (CFT) and the serum agglutination test (SAT). The prevalence among goats was 0.4% and among sheep 0.6%. The prevalence among 183 imported goats and sheep was 4.4%. The sensitivity and specificity of three serological tests available for the diagnosis of brucellosis -CFT, RBPT and SAT - were compared using ovine sera obtained throughout an outbreak of abortion due to Brucella melitensis. The RBPT and the SAT were relatively insensitive compared with the CFT (71 and 44% respectively) and the RBPT was as specific as the SAT when suspicious sera were included. The results suggests that the SAT adds little information when used with other tests and the RBPT has limited applications as a screening test for ovine brucellosis.

Acute Trypanosoma vivax infection in dairy cattle in Coast Province, Kenya

In an outbreak of a fatal haemorrhagic disease in exotic dairy cattle (Friesian, Guernsey, Ayrshire and Jersey) on 2 farms in the Coast Province of Kenya, and investigation was conducted to establish the aetiological agent involved. Blood and lymph node smears made from clinically sick cattle indicated infection with Trypanosoma vivax. Five calves were then experimentally inoculated with heparinised blood from cows naturally infected with T. vivax. All calves had a high T. vivax parasitemia, marked depression and fever; 2 developed blood-tinged diarrhoea 6 and 7 days were treated with isometamidium chloride while others were left untreated. Cases of abortions, bloody diarrhoea and deaths dropped markedly in the treated animals whereas they continued to occur in the untreated animal.