EPIDEMIOLOGICAL STUDIES ON TRYPANOSOMA BRUCEI GAMBIENSE IN BENUE AND TARABA STATES OF NIGERIA

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Date
2014-08
Authors
KARSHIMA, SOLOMON NGUTOR
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Abstract
The aim of this study was to determine the epidemiology of Trypanosoma brucei gambiense infections in Benue and Taraba States of Nigeria using participatory epidemiology, serology, as well as parasitological, entomological and molecular techniques. Of the 1,200 blood samples of humans examined using the card agglutination test for T. b. gambiense (CATT), 21 were positive giving an overall human sero-prevalence of 1.75%. State based sero-prevalence rates were 1.3% (8/600) for Benue and 2.2% (13/600) for Taraba States. Local Government Area based seroprevalence rates in Benue were 0.8% (5/600), 0.5% (3/600) and 0% (0/600) for Gboko, Vandekya and Ukum respectively, while, Gashaka, Ibi and Karim Lamido in Taraba recorded sero-prevalence rates of 1.2% (7/600), 0.2% (1/600) and 0.8% (5/600) respectively. Gender based sero-prevalence rates in Benue were 1.0% (6/600) for males and 0.3% (2/600) for females while in Taraba, 1.33% (8/600) and 0.83% (5/600) were recorded in males and females respectively. There was no significant association between the sex based prevalence rates (p>0.05). Age based sero-prevalence rates in Benue was 0.67% (4/600) for both children and adults, while, children and adults in Taraba recorded sero-prevalence rates of 1.2% (7/600) and 1.0% (6/600) respectively. There was no significant association between the age based prevalence rates (p>0.05). Out of the 1,200 blood samples of animals examined using the CATT, 107 were positive, giving an overall animal sero-prevalence of 8.9%. Of this, pigs and cattle recorded sero-prevalence rates of 10.7% (64/600) and 7.2% (43/600) respectively. Highest seroprevalence rates in Benue and Taraba were observed in Gboko 5.7% (34/600) and Gashaka 3.7% (22/600) Local Government Areas respectively. There was significant association between the LGA based prevalence rates (p<0.05). Management based sero-prevalence rates were 8.7% (52/600) for extensively managed and 2.0% (12/600) for intensively managed pigs. Breed based sero-prevalence rates in cattle were 5.33% (32/600), 1.5% (9/600) and 0.33% (2/600) for White Fulani, Bokoloji and Muturu respectively. There was significant association between the breed based prevalence rates (p<0.05). Sex based sero-prevalence rates were 4.7% (28/600) in females and 6.0% (36/600) in males for pigs as well as 2.83% (14/600) in males and 4.83% (29/600) in females for cattle. The highest tsetse catch in Benue and Taraba were in Gboko 78/531 (14.7%) and Gashaka 226/531 (42.6%) respectively. Two species of tsetse flies identified during the study were Glossina palpalis 87.2% (463/531) and Glossina tachinoides 12.8% (58/531) with infection rates of 3.4% and 1.2% respectively. A total of 11 Trypanosoma isolates of which 6 (54.5%) originated from humans, 3 (27.3%) from pigs and 2 (18.2%) from cattle were characterized by the identification of internal transcribed spacer-1 (ITS-1) rDNA, serum resistance antigen (SRA) and Trypanosoma gambiense specific glycoprotein (TgsGP) genes. Kinetoplastids (KIN) primer sets identified all the 11 purified Trypanosoma isolates from mice blood giving 100% sensitivity. The KIN primer sets identified all human isolates as belonging to the T. brucei genome, while in animal samples both T. brucei and T. congolense were identified. ITS-1 primer sets identified T. brucei, T. congolense forest and T. congolense savannah subspecies from isolates of cattle and pig origin. PCR targeting serum resistance antigen gene excluded the presence of human infective T. b. rhodesiense in all the 6 human and 5 animal isolates. A strain-specific TgsGP primer set characterized all the 6 human, 1 cattle and 2 swine isolates as type 1 T. b. gambiense. Of the 30 tsetse blood-meals analyzed for the identification of their sources of blood-meals, 10 (33.3%), 9 (30.0%), 7 (23.3%) and 4 (13.3%) fed on cattle, pigs, dogs and humans respectively. The differences between the feeding frequencies of tsetse on the individual vertebrates showed no significant association (p>0.05). There were mixed feedings involving human-cattle-pig-dog among 2 (6.7%) and cattle-dog-pig among 5 (16.7%) of the analyzed tsetse flies. Dual feeding patterns involving human-dog 2 (6.7%), human-cattle 4 (13.3%) and human-pig 3 (10.0%) were also observed. There were no significant associations between tsetse feeding frequencies on both multiple and dual feeding patterns (p>0.05). The respondents in the participatory epidemiology rated HAT among seven other endemic diseases to have the highest mortality of 85.0% (34/40) and economic impact of 70% (28/40). Wildlife species, domesticated animals and humans were identified by participants as reservoirs of T. b. gambiense and their proportionate ratings in disease transmission were 34/40 (85.0%), 28/40 (70.0%) and 7/40 (17.5%) respectively. Game reserves and homestead areas were assigned the highest and lowest sources of infection with proportions of 29/40 (72.5%) and 10/40 (25.0%) respectively. Farming was identified by respondents as the major risk occupation while shepherding was considered the least risk occupation with proportions of 30/40 (75.0%) and 7/40 (17.5%) respectively. The age brackets 16-30 and >75 years were considered as having the highest 33/40 (82.5%) and lowest 3/40 (7.5%) HAT impacts in the studied communities. The findings of this study have established the presence of T. b. gambiense type 1, forest and Savannah sub-species of T. congolense, the roles of animal reservoirs, species-specific, dual and mixed feeding patterns of tsetse flies in the epidemiology of HAT in the study areas
Description
A DISSERTATION SUBMITTED TO THE POST-GRADUATE SCHOOL, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF THE DEGREE OF DOCTOR OF PHILOSOPHY IN VETERINARY PUBLIC HEALTH AND PREVENTIVE MEDICINE. DEPARTMENT OF PUBLIC HEALTH AND PREVENTIVE MEDICINE, FACULTY OF VETERINARY MEDICINE, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA AUGUST, 2014
Keywords
EPIDEMIOLOGICAL,, TRYPANOSOMA,, BRUCEI,, GAMBIENSE,, INFECTIONS,, TARABA STATES.
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