EPIDEMIOLOGY OF HUMAN BRUCELLOSIS IN OYO STATE OF NIGERIA

Abstract

Brucellosisis a zoonosis, primarily a disease of domestic animals which under special circumstances, may be readily transmitted to man. The epidemiological picture of the disease varies from area to area in different parts of the world and has to be studied carefully in planning control and eradication programmes. In Nigeria, where livestock management is still largely unscientific and bovine brucellosis is known to be endemic (Esuruoso, 1975b), there are only scanty data on the epidemiology and clinical presentation of man brucellosis. Therefore, the present study, which covered a period of three and half years between September 1973 and February 1977, was undertaken with the objectives of collecting adequate and reliable data on the epidemiology of human brucellosis in Oyo State of Nigeria in order to be able to formulate a realistic control programme. The study also aimed at expanding medical and applied scientific knowledge in the field of brucellosis and occupational medicine in Nigeria. Over 70 per cent of the total 55 million Nigerians (1963 census report) live in rural areas and form settlements. Medical and other social services are grossly inadequate in the whole country and the few amenities are concentrated in the capital cities and other big towns, with the rural agricultural areas virtually neglected. Agriculture is the mainstay of the Oyo State economy, and approximately 5 per cent of the State’s labour force are engaged in agricultural work. Cow meat is the most readily available animal protein to the people of Oyo state, the resent epidemiological study was undertaken largely in several farm settlements over Oyo state, but the central based at the Department of Medical Microbiology. University college hospital, Ibadan, where also the clinical aspects of the study were carried. The pilot sero- epidemiological evaluation on human brucella antibodies carried out on 1600 people of various occupation and age groups living in Ibadan, capital of Oyo State, revealed on overall sero-positivity rate of 50.2 per cent. Significantly higher prevalence of infection was found among the occupationally exposed peculation including herdsmen, abattoir workers and veterinarians, than the general population, including blood donors, pregnant women and school children. The important identifiable sources of human infection include direct transmission from infected animal through abraded skin, nasopharyngeal mucosa and the conjunctives. Other sources of human infection are by ingestion of infected milk, especially on the ferms, or eating of roast meat (barbecue), which is becoming popular at portion among the cities in the urban centres. Further epidemiological investigations carried out In several livestock farms showed that the important factors determining the rate and level of human brucellosis in Oyo State include: (1) the geographical location of the form; (2) the number of cattle per head of population and the frequency or contact with infected animals; (3) the rate of active infection in the cattle herd; (4) the system of animal husbandry: whether scientific or traditional methods; and (5) imported bovine Infection from neighboring countries. An outbreak of active bovine brucellosis with human involvement which was investigated during the study revealed that the hazards caused by Br,abortus infections are of great social and pubic heath important in Oyo state. The economic loss to the livestock industry due to brucellosis if estimated, would run into millions of naira (#) annually, judging from the high rate of abortion and infertility among heifers in some farms. The public health consequences are also enormous, considering the fact that protein undernutrition is very common in Nigeria (Morley, 1973), especially in the rural areas (oyenuga 1976) and the ill-health which prevents the farmers from taking proper care of their livestock. An economically viable livestock industry will be difficult to achieve under the present stage of endemic brucellosis in Oyo state. The practical problems of controlling brucellosis in a developing economy were highlighted, as the ideal slaughter technique leading to eradication of bovine infection is not feasible because of the present poor state of livestock industry in Oyo state. However, realistic control measures, based on the improvement of the existing agricultural, social, and health systems in the state, are possible. Immediate inter-control measures include hygiene on the farm and abattoirs, avoidance of raw milk and introduction of vaccination programmes for beef cattle in settled herds. In addition, every effort should be made to improve the social and medical services in the rural areas of the state. The long-term control measures should include the establishment of clinical and laboratory services, health education of farmers and abattoir workers, full coordination in the medical and veterinary services, widespread pasteurization of fresh milk, the establishment of a state-federal co-operative Brucellosis control programme, and finally industrial for the improvement of the working conditions of the livestock farmers. The suggested future studies which are directly indicated from the present study include (1) large scale epidemiological survey of Nigeria to determine the overall socio-economic significance of human brucellosis, and therefore, to formulate a national control program, (2) further evaluation of the role played by brucellosis among patients with pyraxis of undetermined origin, pregnant women with second –trimester abortions and patient with neuro-psychiatric disorder and (3) production of safe and effective human immunizing agent against brucellosis, especially among the occupationally exposed individuals in areas with endemic bovine disease.