http://hdl.handle.net/123456789/134 2026-04-08T07:17:21Z 2026-04-08T07:17:21Z OKE, PHILIP OLADELE http://hdl.handle.net/123456789/2224 2024-04-26T16:07:26Z 2023-03-01T00:00:00Z

MORPHOLOGICAL AND MOLECULAR IDENTIFICATION OF CULICOIDES SPECIES, THEIR HOST PREFERENCE AND INVOLVEMENT IN THE TRANSMISSION OF FILARIAL PARASITES IN BENUE STATE, NIGERIA OKE, PHILIP OLADELE Culicoides (biting midges) are small blood-sucking dipteran flies inhabiting various regions of the world. They are biological vectors of numerous economically important pathogens, especially filarial nematodes and a serious source of annoyance to humans and animals. Despite their importance and status as neglected vectors, there is limited information on morphology and molecular identification of Culicoides species in Nigeria, especially Benue State. Therefore, this study was aimed at identifying Culicoides species, their host preference and their possible involvement in filarial worm transmission in Benue State, Nigeria. A purposive sampling technique was used for the collection of adult Culicoides species in thirty locations across the three geopolitical zones (Benue South, Benue Northeast, and Benue Northwest) in Benue State, Nigeria. In weekly overnight collections using two CDC black-light suction traps, Culicoides species were trapped between January and December, 2018 and corresponding environmental data recorded. The trapped Culicoides were morphologically identified using a stereomicroscope to determine their sex and parity status. Polymerase chain reactions were carried out and characterisation of dominant species was achieved using sequence analysis targeting the ITS1 gene. Their sources of blood meals were investigated using mitochondrial MT-cyt b gene and their role in the transmission of filarial parasites was probed using Cox-1 gene. Data were analysed using descriptive statistics and correlation coefficient at α0.05. A total of 30,163 Culicoides species were trapped, with the highest collection of 13,700 (45.4%) recorded for Benue South geopolitical zone. There was positive association between rainfall and the number of Culicoides species trapped (r = 0.96), while the number of catches correlated negatively with wind speed and temperature (r = -0.1586 and r = - 0.4789) respectively. Twenty-one species were morphologically identified. Females represents 87.9% (n = 26,502) of the total collection of which 31.4% (n = 8,314) were parous. The two dominant species were Culicoides imicola (37.6%) and C. oxystoma (13.8%). Culicoides indistinctus (0.2%) identified in this study area is a new species reported in Nigeria. The Nigerian C. imicola and C. indistinctus strains were 95.8% and 97.3% related to French strains respectively, while C. oxystoma was (95.2%) related to Israeli strains. Cattle (60%), humans (37%) and dogs (3%) were their preferred hosts. The filaria, Onchocerca gutturosa was found in C. imicola and C. oxystoma that fed on cattle, while Mansonella perstans was obtained only from C. oxystoma that fed on humans. Culicoides imicola and Culicoides oxystoma were dominant species while Culicoides indistinctus was identified for the first time in Nigeria. The potential roles of Culicoides in the transmission of filarial parasites of humans and animals were confirmed. Hence, control of Culicoides is recommended.

2023-03-01T00:00:00Z ODENIRAN, PAUL OLALEKAN http://hdl.handle.net/123456789/1404 2022-02-22T09:00:05Z 2020-01-01T00:00:00Z

TRANSMISSION PATTERNS OF TRYPANOSOMES IN FLY VECTOR POPULATIONS AND BOVINE HOST IN SOUTHWESTERN NIGERIA ODENIRAN, PAUL OLALEKAN Bovine trypanosomosis is still a major health problem causing severe morbidity and mortality, and the control of the disease is centered on Glossina, the main vector. Information on other vectors (Tabanus and stomoxyine) transmitting trypanosomes in southwestern Nigeria are lacking. This study was designed to investigate the transmission patterns of trypanosome in vectors and cattle to enable an effective control strategy. Fifteen cattle settlements and institutional farms in the six southwestern states were randomly selected and Nzi traps set to capture transmitting vectors between April 2016 and March 2017. The vectors were identified using morphology, 28S rRNA PCR and Sanger sequencing. Fly abundance with environmental variables, distribution, endosymbionts, bloodmeal sources and feeding behaviour were investigated using standard methods. Insecticidal effects of cypermethrin against fly vectors were assessed using standard methods. Blood (125 µL) was randomly collected from 745 cattle during the same period in some of the locations. The vectors and cattle blood were screened for trypanosomes using 18S rRNA PCR, while Trypanozoon DNA positives were screened for RoTat 1.2 VSG and TgsGP genes. Livestock owners (n = 209) were interviewed using structured questionnaire to determine control methods. Relevant publications in databases from 1960-2017 were screened using PRIMSA checklist to analyse the southwest Nigeria estimates of trypanosome prevalence in livestock and Glossina. Data were analysed using descriptive statistics and one way ANOVA at α0.05. The identified transmitting vectors belong to the genera Glossina, Tabanus and Stomoxys. The total apparent density of trapped flies [Glossina (0.6 flies/trap), Tabanus (0.2 flies/trap), Stomoxyine (36.2 flies/trap)] was highest at temperature of 26-28°C, humidity >80.0% and rainfall of 150-220 mm/month. Distribution of flies increased with vegetation density and decreased in areas with high human population density (>100/km2 ). Sodalis glossinidus (31.3%) was the only endosymbiont in Glossina. Sequenced cytochrome-B mitochondrial DNA segments revealed eight different host species as bloodmeal sources. On the average 78.0%, 19.6% and 10.2% Glossina, Tabanus and Stomoxyine, respectively were fully engorged. Cypermethrin was effective on Stomoxyine using restricted insecticidal application protocol, but ineffective using conventional pour-on protocol. Overall, 71.1%, 33.3% and 22.2% Glossina, Tabanus and Stomoxyine, respectively were positive for trypanosomes. Trypanosomes were identified in Glossina (T. vivax 36.4%, T. brucei 53.5%, T. congolense viii 5.4% and T. simiae 4.7%), Tabanus (T. vivax 43.5%, T. evansi 39.1%, T. simiae 8.7% and T. godfreyi 8.7%), and Stomoxyine (T. vivax 69.2%, T. evansi 20.5%, T. congolense 5.1% and T. simiae 5.1%). Trypanosome DNA was detected in 23.8% of cattle examined with significant increase in Osun State compared to other states. The species identified were T. vivax (43.4%), T. congolense (31.8%), T. brucei (18.2%) and T. evansi (6.6%). Livestock owners (93.9%) used trypanocides, while 60.5% used insecticides. Published articles revealed overall prevalence of bovine trypanosomosis at 21.3% and trypanosome prevalence of 42.6% from 4,808 Glossina species. The mechanical vectors (Tabanus and Stomoxyine) are as important as biological vector (Glossina) in the transmission of bovine trypanosomosis in southwest Nigeria. The distribution and vectorial capacity of captured vector species warrants a new effective control strategy against trypanosomes.

2020-01-01T00:00:00Z