The epidemiology of brucellosis in animals and humans in Arusha and Manyara regions in Tanzania

Shirima, Gabriel Mkilema (2005) The epidemiology of brucellosis in animals and humans in Arusha and Manyara regions in Tanzania. PhD thesis, University of Glasgow.

Abstract

The aims of this study were to assess community knowledge, awareness and practices on
zoonoses, to gather baseline data on brucellosis in livestock and wildlife, to establish
brucellosis seroprevalence in domestic ruminants and humans and risk factors associated
with livestock seropositivity, to assess brucellosis dynamics and impact on livestock
production and reproduction and to evaluate the performance of the Rose Bengal Plate Test
(RBPT) in Tanzania. The results described in this study were carried out through
Participatory Rural Appraisal (PRA), cross-sectional and longitudinal studies.
In the PRA and cross-sectional studies, rabies, tuberculosis, anthrax and brucellosis were
the zoonoses most frequently identified. Cattle were frequently identified as being
associated with tuberculosis, anthrax and brucellosis, whereas dogs were frequently
identified as being associated with rabies. Small ruminants, pigs, cats and poultry were
either infrequently, or not identified as being associated with zoonoses. Recognition of
clinical signs of zoonoses in humans was better than in animals. Ingestion of animal
products was a route frequently identified as transmitting zoonoses to humans.
During the baseline serosurvey, seroprevalences for brucellosis were 6.2% in cattle, 6.5%
in small ruminants and 13% in wildlife, respectively. Seropositivity was significantly
higher in the pastoral (13.2%), followed by agro-pastoral (5.3%), and lowest in the small
holder dairy system (2.3%) (p<O.05).
During the cross-sectional serosurvey, the seroprevalence was significantly higher in older
animals and large herds (p<O.OOl). Variation in seropositivity between households was higher (1-30%) in the pastoral compared to agro-pastoral (1-14%) households. The model
that best explained c-ELISA seropositivity included the feeding of dogs with foetuses and
placentae, calving during the wet season, and the fanning system.
In humans, 28% of families were seropositive for brucellosis with the highest levels in
Ngorongoro district (46%), and lowest in Babati district (0%). Families with seropositive
herds were 3.3 times more likely to be seropositive. However, 25% of families were
seronegative when their herds were seropositive, and 48% of families were seropositive
with seronegative herds.
In the longitudinal study, the incidence was 73211,000 cases per animal-years at risk with
an estimated survival probability of 0.836. Households with a high seroprevalence at the
initial sampling had a high incidence of seroconversion in the subsequent visits.
Occurrence of new seropositive cases was significantly higher in the wet season (p< 0.05).
Calf serostatus was statistically associated with dam serostatus but no significant
difference in growth rate was observed between calves suckled from seropositive and
seronegative dams.
Brucella melitensis type-1 was isolated from goats' milk following culture. Blood and
placenta samples were negative on bacteriological culture. The RBPT was found to have
low sensitivity in both field and laboratory settings.
Brucellosis infection in livestock is widespread, but poses the greatest risk to human health
and livestock production in pastoral systems in Tanzania.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: S Agriculture > SF Animal culture > SF600 Veterinary Medicine
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Supervisor's Name: Cleaveland, Dr. Sarah, Fitzpatrick, Prof. Julie L., Kambarage, Prof. D.M. and Kazwala, R.R.
• Date of Award: 2005
• Depositing User: Ms Mary Anne Meyering
• Unique ID: glathesis:2005-4826
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 13 Jan 2014 16:57
• Last Modified: 13 Jan 2014 16:58
• URI: https://theses.gla.ac.uk/id/eprint/4826