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