Evaluation of slide test, 2-mercaptoethanol test and Elisa in diagnosis of human brucellosis in Nyandarua Distrit, Central Provine, Kenya

Brucellosis is a zoonotic disease caused by organisms in the genus Brucella, and has a worldwide distribution. Brucella abortus, B. ovis, B. suis and B. melitensis are pathogenic to man, and human infection occurs through contact with infectious blood, urine, placenta and or aborted foetus and consumption of raw contaminated animals products such as milk, cheese and blood. Diagnosis of brucellosis is difficult because clinical manifestations can be misleading, culture lack sufficient sensitivity and require prolonged incubation leading to excessive delay in diagnosis while serological tests are difficult to interpret. This leads to misdiagnosis and the need to evaluate the performance of laboratory diagnostic methods (Slide test, 2-Me and ELISA) in terms of sensitivity, specificity and predictive values. Factors that predisposes humans to Brucella infection as well as the level of awareness about the disease particularly symptoms, treatment and prevention in the. study population need to be known for public health appraisal. The study population comprised of all who were residents of Nyandarua district and a sample size of 180 studied. The prevalence of human brucellosis was 3.9%. While 2-Me and ELISA had the same sensitivity, there was a statistically significant difference in sensitivity of Slide test compared to both 2-Me and ELISA; Z actual (20.05» Z expected (2.33 at P = 0.01). A statistically significant difference existed between specificity of Slide test compared to 2-Me [Z actual (3.81) > Z expected (2.33 at P = 0.01)] and ELISA [Z actual (3.54) > Z expected (2.33 at P = 0.0 I)]. 2-Me had a statistically significant higher positive predictive value compared to Slide test [Z actual (10.7) > Z expected (2.33 at P = 0.01)] as was ELISA compared to Slide test [Z actual (18.73) > Z expected (2.33 at P = 0.01)]. There W:1S no statistically significant difference between negative predictive value of Slide test compared to both 2-Me and ELISA; Z actual (0.53) < Z expected (2.33 at P = 0.01) and Z actual (0.47) < Z expected (2.33 at P = 0.01) respectively. Consumption of contaminated animal products was found out to be the major route of transmission in Nyandarua district while awareness pertaining brucellosis symptom, prevention and treatment in the district was found to be low. It is recommended that Slide test be only used for screening while SAT, 2-Me and ELISA may be used as confirmatory tests and 2-Me test be incorporated in routine diagnosis. Further it is recommended from the findings of this study that the government through the Ministry of Public Health creates awareness of brucellosis to the public to strengthen its control and po-sible eradication. CHAPTER ONE INTRODUCTION 1.1 Background information Brucellosis is a zoonotic disease affecting both man and a wide range of wild and domestic animals such as livestock, rodents, whales, dolphins and seals, and wild ruminants (Talaro, 2005) and has a worldwide distribution. The disease. also referred to as Malta fever, undulant , fever or Bang disease is caused by organisms in the genus Brucella (Kumar and Clark, 2004). Brucellosis is associated predominantly with occupational contact in slaughterhouses, livestock handling and the veterinary services (Antonio et al., 2005). High concentrations of the disease occur in Europe. Africa, India and Latin America. It has been virtually eliminated from cattle in the UK, but high prevalence still occurs in Mediterranean countries, the Middle East and the tropics, where about 500.000 new cases are reported per year (Kumar and Clark, 2004). Cook and Zumla (2003) pointed out that in the tropics, cases of brucellosis occur predominantly in rural areas among pastoralist people and also occur in urban settings where small numbers of animals are kept in and around the homestead. Human infection occurs through contact with infectious blood. urine, placenta and or aborted foetus and consumption of raw contaminated milk and cheese. Brucella organisms enter the body via damaged skin or mucous membrane of the digestive tract, conjunctiva and respiratory tract (Talaro, 2005). Though person-to-person transmission is rare, spread through sexual contact and by tissue transplant has been reported (Greenwood et al., 2002). The true prevalence of human brucellosis is not accurately known. Reported prevalence in disease endemic areas varies widely from 0.01 to 200 cases per 100,000 persons (Cook and Zumla, 2003). The true prevalence of brucellosis is several times greater than the reported KfNYATTA U~t1VERSITYLIBRAR~