|Year : 2019 | Volume
| Issue : 14 | Page : 64-67
Biting preferences of blackfly in two endemic communities of ose local government area, Ondo state, Nigeria
Olajide Joseph Afolabi
Department of Biology, Federal University of Technology, Akure, Nigeria
|Date of Submission||01-Dec-2018|
|Date of Acceptance||01-Jun-2019|
|Date of Web Publication||04-Oct-2019|
Dr. Olajide Joseph Afolabi
Department of Biology, Federal University of Technology, Akure
Source of Support: None, Conflict of Interest: None
Context: Blackflies are hematophagous dipterans who transmit Onchocerca volvulus; the pathogen of onchocerciasis. Aims: The study was undertaken in Imeri and Idogun to evaluate the knowledge of respondents on the biting preferences of blackflies. Settings and Design: The design is an observational study in epidemiology which involves the use of structured questionnaire to obtain useful epidemiological information from the respondents. Materials and Methods: Structured questionnaire was administered during personal interview and focus group discussion to obtain useful epidemiological information. Statistical Analysis Used: Data obtained were analyzed using Carl Pearson Chi-square at P < 0.05 level of significance. Results: The results showed that only 193 of the 578 respondents interviewed in the two communities had adequate knowledge of the cause and mode of transmission of onchocerciasis. This group knew that the disease is transmitted by the bite of infected blackflies. Other respondents (66.6%) had wrong perception about the cause and mode of transmission of the disease. The wrong perceptions observed in the communities include transmission by sexual intercourse, stepping on charms, and transmission from infected parent to offspring. The knowledge on the biting preference of the blackflies as tested among 193 respondents that were knowledgeable about the disease varied significantly (P = 0.05). Some respondents believed the fly bites in the farm (48.7%) and others believed the fly bites by the riverside (36.3%), in the village (5.2%), whereas 9.8% of the respondents believed the fly bites both on the farm and the riverside. Similarly, others believed the fly bites on the exposed legs (54.4%), hands (9.9%), and face (6.7%). Meanwhile, 29% of respondents believed the fly bites on any exposed part of the body. Conclusions: The results revealed that ignorance on the bioecology of the vector is still very high in these communities.
Keywords: Bioecology, blackfly, onchocerciasis, preference
|How to cite this article:|
Afolabi OJ. Biting preferences of blackfly in two endemic communities of ose local government area, Ondo state, Nigeria. N Niger J Clin Res 2019;8:64-7
|How to cite this URL:|
Afolabi OJ. Biting preferences of blackfly in two endemic communities of ose local government area, Ondo state, Nigeria. N Niger J Clin Res [serial online] 2019 [cited 2019 Dec 5];8:64-7. Available from: http://www.mdcan-uath.org/text.asp?2019/8/14/64/268535
| Introduction|| |
Hematophagous insects such as blackflies are known to be biological vectors of man and animal parasites. The blackfly of the family Simuliidae transmits parasite (Onchocerca volvulus) when sucking blood from its host. The blood is required for the maturation of the eggs in the female fly. The family Simuliidae contains several genera, one of which, Simulium, is an important human-biting fly, known as the biting blackfly or buffalo fly. Blackflies are small insects that measure 1–5 mm in length and possess a shiny thorax that ranges in color from black to various shades of gray or yellow. The pathogen (O. volvulus) transmitted by the blackfly is the causative agent of onchocerciasis. O. volvulus is a filarial worm that resides in the subcutaneous tissues of the host where it triggers both ocular and dermal manifestations. The immature stages of filarial worms cannot mature to adulthood without being transmitted by a blackfly of the genus Simulium. This makes the blackfly an essential vector in the transmission of onchocerciasis. The observable clinical manifestations in human are caused by the microfilaria stages of O. volvulus, with inflammation and tissue damage mostly seen when the parasite is dying or being destroyed by the drug and/or host responses. Another factor that could contribute to the development of pathology and clinical manifestations of onchocerciasis is the obligatory endosymbiotic bacterium Wolbachia, which has been rediscovered and found to be abundant in all developmental stages of the O. volvulus.,, The genus name Onchocerca is derived from the Greek word “Ogkos” which means swelling and “kerkos” which means tail. Two strains of O. volvulus exist in West Africa; the Savannah strain which is found in the West African Savannah and is characterized with mild form of onchocercal dermatitis, more ocular infection, high microfilarial loads, and palpable nodules prevalence. Moreover, the forest strain which is endemic in the West African rainforest which appears to induce less ocular infection, severe dermal pathology, low microfilarial loads, and less palpable nodules. Onchocerciasis also known as river blindness, which is the leading cause of preventable blindness and a severe pruritic skin condition in endemic areas. The disease is most prevalent in Africa and Nigeria, probably has the highest burden of the disease. The disease affects about 10 million people living in scattered foci in the Savannah and Rain forest regions of Nigeria. The transmission of onchocerciasis is restricted to the riverbanks, and communities around the riverbank suffered from severe infection. The transmission is localized to the riverbanks because the vector (blackflies) breed in fast flowing rivers (well-oxygenated rivers) and have a short flight range. Simulium can fly for up to 80 km in 24 h along the water sources by the aid of their strong thoracic muscles. At times, they went 100 km from one river basin to another. Blackflies have a preference for a wide range of individual hosts. Some people are very attractive to blackflies and exhibit strong feeding reactions. Others appear to repel blackflies and are bitten little. Human usually acquires the infection after being bitten by blackflies of the Simulium damnosum carrying infective larvae of the O. volvulus. This current study intends to evaluate the knowledge of respondents on the biting preferences of blackflies in endemic communities of Ose Local Government Area, Ondo State, Nigeria.
Comment: The introduction is insufficient. The authors should expand on the introduction.
Action on comment: The introduction has been expanded as suggested by the reviewer. The corrections were highlighted in blue color.
| Materials and Methods|| |
The study was conducted along River Ose, South Western Nigeria. River Ose lies on the latitude 07°56'N and 07°34'N, longitude 03°06'N and 03°36'E in the forest zone of Nigeria, and transverse through Ondo and Edo States. Imeri and Idogun are communities along the River Ose that were considered for this study. The two communities are characterized by the forest vegetation. There are over 140,000 inhabitants living in the Ose Local Government Area where the river transverse. The major occupations along the Ose river are; fishing, lumbering, hunting, and farming. Meanwhile, farming is the predominant occupation along the river, and most farmers use water from the river to irrigate their farms. The study area has two seasons: the wet season (April–October) and the dry season (November–March).
Prior to the commencement of the study, approval for the study protocol was obtained from the Department of Disease Control of the Ondo State Ministry of Health, Ose Local Government Area, and Community Heads of Imeri and Idogun. Likewise, the informed consent of the respondents was obtained before they were recruited to participate in the study. The respondents were enlightened on the benefits of their participation in the study.
Structured questionnaires were administered to the respondents above 10 years of age, after focus group discussion in the local dialect. The questionnaires were used to test respondents' knowledge on the biting preferences of the vector (blackfly). Demographic data such as age, sex, and occupation were obtained by the questionnaires.
| Results|| |
[Table 1] showed that only 193 (33.4%) had adequate knowledge of the disease as they were able to mention that the disease is transmitted by the bite of the blackfly carrying the infective stage of the parasite. Large percentage of the respondents (66.6%) believed that the disease is caused by other means such as sexual intercourse (n = 30, 5.2%), stepping on charms (n = 45, 7.8%), inherited (n = 60, 10.4%), old age (n = 79, 13.7%), lack of personal hygiene (n = 43, 7.4%), and too much farm work (n = 58, 10.0%). Seventy respondents (12.1%) had no idea of the cause and mode of transmission of the disease. This suggests that the responses of respondents on the cause and mode of onchocerciasis in the two communities are significantly different (t value = 5.639; P = 0.001, P < 0.05).
|Table 1: Respondents' knowledge about cause and mode of transmission of onchocerciasis in Imeri and Idogun communities|
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Knowledge of the biting preference of the blackfly among the respondents in Imeri and Idogun communities
[Table 2] evaluates the knowledge of respondents on the biting preference of the onchocerciasis vector (S. damnosum). This knowledge was tested among the 193 respondents that are knowledgeable on the cause and mode of transmission. These are the individuals that knew that the disease is transmitted by the bite of infected blackflies. Most respondents (36.3%, n = 70) in communities believed that the blackfly bites often by the riverside and as such believed avoiding the riverside should be the best way to prevent the disease. Likewise, 48.7% (n = 94) of the respondents in these communities (Imeri and Idogun) were of the opinion that the blackfly bites mostly at the farm and believed that the disease is common among the farmers. Whereas, 9.8% (n = 19) of the respondents believed that the fly could bite both on the farm and the riverside. In contrast, 5.2% (n = 10) of the knowledgeable respondents believed the fly usually bites people in the village [Table 2]. The biting periods of the blackfly as perceived by the respondents in the two communities varied significantly (χ2 = 23.091, P = 0.000, P < 0.05). Forty-four of the respondents (22.8%) believed the fly bites in the morning hours, 11.9% (n = 23) believed the fly bites in the afternoon, 6.2% (n = 12) believed the fly bites often in the evening, and largest percentage (59.1%, n = 114) of the respondents believed that the fly can bite anytime of the day [Table 3]. Furthermore, seasonal variation in the biting preference of blackfly was reported by the respondents in these communities. Most respondents in the communities (87.1%, n = 168) believed the fly bites only in the wet season, while 5.2% (n = 10) of the respondents believed the fly bites only in the dry season. However, 15 individuals (7.7%) were of the opinion that the blackfly bites both in wet and dry seasons [Table 4].
|Table 2: Respondents' knowledge on biting preference of the blackfly in Imeri and Idogun communities|
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|Table 3: Respondents' knowledge on biting period of the blackfly in Imeri and Idogun communities|
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|Table 4: Respondents' knowledge on biting season of the blackfly in Imeri and Idogun communities|
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In addition to the biting sites, periods, and seasons, the respondents in these communities also believed that the blackfly has a preference for different parts of the body. For instance, largest percentage (54.4%, n = 105) of the respondents believed the blackfly preferred the exposed leg, 9.9% (n = 19) believed the blackfly preferred the exposed hand, 6.7% (n = 13) believed the fly preferred the face, and 29% (n = 56) of the respondents believed the blackfly does not have any preference for any part but bites any exposed parts of the body [Table 5].
|Table 5: Respondents' knowledge on preferred biting parts of the blackfly in Imeri and Idogun communities|
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| Discussion|| |
The results of the bioecology of the blackflies revealed that some of the respondents in these communities believed that the fly transmits the parasite (O. volvulus) through biting while taking blood meal from the host. Nevertheless, the perceptions varied significantly among the respondents in these communities (P = 0.05). The knowledgeable individuals in these communities also believed that the blackfly bites mostly on the farm and by the riverside. This suggests that the respondents believed that swimming, washing, and fishing in the river, as well as farming around the river, would expose individuals to high risk of onchocerciasis. This finding has been supported by the results of other authors., The knowledgeable respondents also believed that avoiding contact with the river would be the best way to avoid the disease in their communities. Nevertheless, the respondents agreed that it would be practically impossible for them to completely stay away from the river, especially during the dry season when the few wells in the communities run dried. Therefore, suggests that the provision of public water such as boreholes and pipe-borne water in the communities will help to reduce human to vector contact and as such drastically reduce the prevalence of river blindness in these communities. The knowledge of the patients on the biting preference as observed in the communities during the study showed that many of the patients believed that the fly could bite anytime of the day and do so mostly in the wet season. They also believed the fly had preference for the lower limbs of the host than other parts of the body. Therefore, fishermen, lumbermen, hunters, and farmers that work around the riverbank should endeavor to wear long sleeves and trousers when going about their occupation. This will help to reduce the human to vector contact and as such reduce the menace of onchocerciasis in these communities. The significant difference in the biting preference, biting periods, and biting parts had also been observed by Dozie et al. in Imo State and Adeleke et al. in Osun State.
| Conclusions|| |
The ignorance of the residents of the two communities, especially on vital information regarding the bioecology of the blackfly may be a major impediment to the effective control of onchocerciasis in these endemic communities. This ignorance might be one of the factors that determine the prevalence of infection in these communities. Therefore, to achieve a meaningful progress in disease control and prevention and health education, especially in local languages, should be intensified in endemic areas.
The author would like to acknowledge the contribution of Dr. O.O Olawanle, the Public Health Coordinator of Ose Local Government, for the permission to use the public health centers in Imeri and Idogun.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]