Short communication

Prevalence of brucellosis in crossbred and indigenous cattle in Tanzania

E D Karimuribo*, H A Ngowi, E S Swai** and D M Kambarage

Sokoine University of Agriculture (SUA), Department of Veterinary Medicine and Public Health, P.O. Box 3021, Morogoro, Tanzania
*Current address: Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian EH26 0PZ, Scotland, UK
**Veterinary Investigation Centre (VIC), P.O. Box 1068, Arusha, Tanzania
esron.karimuribo@moredun.ac.uk   /   karimuribo@suanet.ac.tz

Keywords: brucellosis, crossbred cattle, indigenous cattle, Tanzania

Brucellosis is considered by the Food and Agriculture Organisation (FAO), the World Health Organisation (WHO) and the Office International des Epizooties (OIE) as one of the most widespread zoonoses in the world (Schelling et al 2003). The disease in cattle, usually caused by Brucella abortus and occasionally by Brucella melitensis and Brucella suis, is characterised by late term abortion; infertility and reduced milk production as a result of retained placenta and secondary endometritis, and excretion of the organisms in uterine discharges and milk. Full-term calves may die soon after birth. In fully susceptible herds, abortion rates may vary from 30% to 80% (Anonymous 2006), although in some cases, abortions may be more insidious. In bulls, acute or chronic infections of the reproductive tract may occur, causing orchitis, epididymitis, seminal vesiculitis, hygromas, particularly of the carpal joints, especially in chronically affected herds. Man, who acquire infection through consumption of unpasteuralised milk, undercooked or fresh meat and blood and handling of aborted materials and live foetuses without using protective gear, often manifest  anorexia, headache, arthralgia and general malaise and less commonly have insomnia, sexual impotence and constipation.

Brucellosis is widespread in African countries, although with varying prevalence (Thimm and Wundt 1976). The history of this condition in Tanzania dates back to 1927 when an outbreak of abortion was reported in Arusha region (Shirima 2005). Since then, a number of studies have been carried out to establish the disease status in livestock. Surveys have shown the disease to occur in cattle in various regions and zones, with seroprevalence varying considerably.

Brucellosis has been reported to occur at the prevalence of 15.2% in Arusha (Mahlau 1967), 12.2% in Kilimanjaro (Swai et al 2005), 12-14% in Eastern zone (Weinhaupl et al 2000) and 15.2% in Southern zone (Otaru 1985). Mahlau (1967) isolated Brucella melitensis from aborting goats and Brucella abortus in aborting cows in Iringa and Arusha regions, respectively. The majority of these studies were carried out in Tanzania involving parastatal farms and indigenous traditional cattle herds, which were often used purposefully. Only two studies have been carried out systematically in the smallholder dairy sector in Tanzania which include a study carried out in Morogoro and Dar-es-Salaam regions (Swai 1997) and that in Morogoro and Coast regions by Mdegela et al (2004). This indicates that there is still paucity of information about the disease status in the smallholder dairy sector. Therefore, the present study was carried out in order to gather additional information, which is likely to contribute to data that may be used to devise appropriate national strategies for the control of the disease.

The current study was carried out in 1999 in Iringa region (located in the Southern Highlands zone) and in the Coast and Tanga regions (located in the Eastern Coastal zone of Tanzania). Animals sampled were from smallholder dairy farms in Iringa (165 farms) and Tanga (130 farms) regions that were randomly selected from sampling frames of 500 and 3000, respectively. The study also involved seven pastoral traditional herds and one parastatal dairy farm in the Coast region that were purposively selected, based on the willingness of the farmers to participate in the study. The parastatal farm used in the study was located within the neighbourhood of indigenous traditional cattle herds in the Coast region. A total of 2,187 cattle of various ages (> 2 years), sexes and breeds were thus included in this study which included 762 (34.8%) dairy animals from smallholder dairy farms in Iringa (542) and Tanga (220) regions; 1,350 (61.7%) indigenous traditional cattle from pastoral herds and 75 (3.4%) dairy cattle from one parastatal farm. All animals from pastoral herds were of indigenous (Bos indicus) Tanzania Shorthorn Zebu (TSZ) type, while those reared on smallholder or government parastatal farms were crossbred cattle (crosses of Bos indicus and Bos taurus).

Animals were screened for brucellosis by collecting approximately five ml of blood from the jugular vein of each animal into a plain vacutainer tube. Sera were later separated by centrifugation and immediately frozen at around -20^oC until processed. Whereas serum samples from all indigenous cattle were examined using both Rose Bengal Plate Test (RBPT) and Serum Agglutination Test (SAT) in order to assess agreement between the two diagnostic tests, those from crossbred cattle were screened using RBPT alone. Thus, a total of 2,187 sera from cattle were examined by RBPT and 1,349 were subjected to SAT analysis (one indigenous animal had no enough sample for this test). For RBPT, any degree of agglutination was considered as a positive reaction and titre equal to or higher than 1/40 was considered positive for SAT.

Data were analysed using Stata 8.2 for Windows to compute proportions of seropositive animals (stratified by breed and by geographical region where relevant) and their 95% confidence intervals (CI). Statistical significance between variables was examined using P-value at critical probability of P<0.05. In addition, the agreement of the RBPT and SAT in the diagnosis of bovine brucellosis was analysed using kappa statistic (κ).

The results of seroprevalence of bovine brucellosis in indigenous and crossbred cattle are presented in Table 1. Based on RBPT, all pastoral herds were found to been infected, with sero-conversion rates ranging from 1.5% to 17.9% and the average being 6.9%, whereas the seroprevalence of brucellosis ranged from 0.6% to 3.6% in smallholder cattle in Iringa and Tanga regions respectively. The proportion of seropositive crossbred animals in the parastatal farm (2.7%) was low and comparable to that in the smallholder dairy cattle in Tanga region (3.6%). Overall, the proportion of seropositive animals based on RBPT was significantly higher (P<0.05) in indigenous than in crossbred cattle. It was also apparent that the seroprevalence of the disease amongst smallholder crossbred dairy cattle was significantly higher (P<0.05) in Tanga than in Iringa region. The agreement between the RBPT and SAT to detect brucellosis was good (κ = 0.75).  

The low prevalence of brucellosis observed in the smallholder dairy animals in both Iringa and Tanga regions agree with the observations made in studies carried out by Swai (1997) and Mdegela et al (2004). On the other hand, the high proportion of seropositive animals in indigenous herds, albeit existence of differences between herds, conform with results of a recent study in Tanzania which also reported higher prevalence of brucellosis in indigenous TSZ cattle than in crossbred kept by smallholder farmers (Shirima 2005). The differences between pastoral and crossbred animals are possibly attributed to increased contacts of infected herds/animals and non-infected ones in the indigenous traditional farming system, as a result of communal grazing and watering, which become more apparent and acute during the dry period. Continued and uncontrolled movement of indigenous animals in the rural settings in Tanzania is an important factor that facilitates herd-to-herd transmission of infection through pasture and water contamination by aborting animals or following normal calving. Poor disposal systems for aborted materials because of poor community knowledge about the zoonotic implications of the disease and the collapse of the animal health service sector in the rural areas as a result of the privatisation of veterinary services may also contribute to the perpetuation of the disease in the rural areas.

On the other hand, the low seroprevalence in the smallholder animals is likely to be explained by stall feeding that minimises contacts between herds and animals. Nevertheless, the “cut and carry” feeding system of animals that is practiced by many smallholders can serve as a potential risk factor but this is likely to play a role when fodder is collected from areas used by indigenous traditional cattle which encroach the peri-urban and urban settings especially so during the dry season. Although traditional cattle in Tanga were not factored into the current study, interaction between smallholder dairy and traditional cattle in some rural areas may explain the slightly higher seroprevalence in Tanga than Iringa animals. Contacts between traditional cattle and animals in the parastatal farms in the Coast region are likely to be responsible for the higher infection status in the dairy animals in the far. However, more studies are required to elucidate the disease status in areas where this interaction exists and responsible risk factors.

Control of the disease in many countries relies on vaccination and culling of infected animals in order to minimise chances for perpetuation of the infection and for protection of consumers and people that are associated with animal keeping. In Tanzania, vaccination for bovine brucellosis using Brucella abortus S19 was previously practiced in state-owned dairy farms, but this stopped in 1980s due to resource constraints (Shirima 2005). Vaccination continues to be practiced only in government-owned ranches (Mgwira 2006 personal communication). It is important to note vaccination has never been carried out in both the traditional and smallholder dairy sub-sectors in Tanzania.

Therefore, the presence of infection in the animals and since, much of milk from the traditional sector is consumed raw in form of naturally fermented milk as it applies to some quarters of urban centres, there is an urgent need to formulate  sensitisation programmes so as to raise the public awareness about the zoonotic risks associated with milk consumption. Public education should also focus on zoonotic risks associated with abortions, handling of aborted materials and consumption of raw or undercooked blood and meat. Indeed, the evidence of brucellosis in humans in communities in the northern part of Tanzania (Mtui-Malamsha 2001, Kunda 2007) calls for an urgent need to develop public health education programes and to  build disease diagnostic capacities in most of hospitals and health centres in order to assist medical experts to promptly diagnose this disease which symptomatically does not differ very much from  malaria;  the most prevalent disease in the country. It is possible that brucellosis may be a serious health constraint in animal-keeping communities, for which consumption of raw milk is a common practice. Coupled with these initiatives, there is also need to formulate a national strategy that builds and works on the basis of collaboration between veterinary and medical disciplines. It would appear is feasible to implement public health education and vaccination strategies in the smallholder dairy sub-sector, whereas public education may be the only relevant option, as of now, in the traditional sub-sector.

 

Acknowledgements

We are grateful for the financial support granted by the Development for International Development UK (DFID) and for the cooperation of farmers during this study.
 

References

Anonymous 2006 B103 – Brucellosis (Bovine). http://www.spc.int/rahs/Manual/BOVINE/BRUCELLOSISE.HTM  site visited on 10/12/2006.

Kunda J 2007 Epidemiology of human brucellosis in the context of zoonoses in Tanzania. PhD thesis, University of Edinburgh, UK. 

Mahlau EA 1967 Further brucellosis surveys in Tanzania. Bulletin of Epizootic Diseases in Africa 15: 373 - 378.

Mdegela R H, Kusiluka L M J, Kapaga A M, Karimuribo E D, Turuka F M, Bundala A, Kivaria F, Kabula B, Manjurano A, Loken T and Kambarage D M 2004 Prevalence and determinants of mastitis and milk-borne zoonoses in smallholder dairy farming sector in Kibaha and Morogoro districts in eastern Tanzania. Journal of Veterinary Medicine Series B 51: 123-128.

Mtui-Malamsha N J 2001 Epidemiological study of brucellosis in humans and animals in Babati and Hanang districts, Tanzania. Masters dissertation. Sokoine University of Agriculture, Morogoro, Tanzania.

Otaru M M M 1985 Potential zoonotic diseases in the southern zone of Tanzania. In: Proceedings of the 3rd Tanzania Veterinary Association Scientific Conference, Arusha Tanzania 3: 367 - 398.

Schelling E, Diguimbaye C, Daoud S, Nicolet J, Boerlin P, Tanner M and Zinsstag J 2003 Brucellosis and Q-fever seroprevalences of nomadic pastoralists and their livestock in Chad. Preventive Veterinary Medicine 61: 279 – 293.

Shirima G M 2005 The epidemiology of brucellosis in Animals and humans in Arusha and Manyara regions of Tanzania. PhD thesis, University of Glasgow.

Swai E M 1997 Studies on the prevalence of bovine brucellosis and reproductive performance in small-scale dairy cattle herds in Dar es Salaam and Morogoro regions. MSc dissertation, Sokoine University of Agriculture, Morogoro, Tanzania.

Swai E S, Mshanga D, Sanka N P and Marandu N H 2005 Prevalence of bovine brucellosis in smallholder dairy farming area, Moshi, Tanzania. Bulletin of Animal Health and Production in Africa 53: 97 – 105.

Thimm B and Wundt W 1976 The epidemiological situation of brucellosis in Africa. Developments in Biological Standardization 31: 201 - 17.

Weinhäupl I, Schöpf KC, Khaschabi D, Kapaga AM and Msami HM 2000 Investigations on the prevalence of bovine tuberculosis and brucellosis in dairy cattle in Dar es salaam Region and in zebu cattle in Lugoba area, Tanzania. Tropical Animal Health and Production 32: 147 - 154.

Received 26 March 2007; Accepted 2 May 2007; Published 4 October 2007

Go to top