Epidemiology of tree-hole breeding mosquitoes in the tropical rainforest of Imo State, south-east Nigeria.

The study of tree-hole breeding mosquitoes was carried out in the tropical rainforest of Imo State Nigeria (two rural areas and two forest reserves in some parts of Orlu Senatorial Zone) between May-October 2002. Using standard entomological procedures, two macrohabitats (natural tree-holes and bamboo traps) and two microhabitats (leaf axils of cocoyams/pineapples and leaf axils of plantain/banana) were sampled for various mosquito species. Mosquitoes were recovered from all the various biotypes sampled. Types of mosquitoes species encountered, their relative abundance, as well as genera varied significantly during the study (p<0.05). Four genera of mosquitoes: Aedes, Culex, Anopheles and Toxorhynchites were recovered while 16 species of mosquitoes encountered include: Aedes aegypti, Ae. africanus, Ae. simpsoni, Ae. albopictus, Ae. stokesi, Ae. taylori, Ae. apicoargenteus, Culex quinquefasciatus, Cx. nebulosus, Cx. trigripes, Cx. decens, Anopheles gambiae, An. funiestus, An. coustani and Toxorhynchites viridibasis. Most of the mosquitoes showed oviposition preferences for one or more habitats. The presence of Ae. africanus, Ae. simpsoni and Ae. aegypti indicate that the study areas were at risk of yellow fever epidemic. The presence of Anopheles and Culex species ensured endemicity of malaria and filariasis, while the recovery of Ae. albopictus in this region suggests a possible outbreak of dengue fever in future if not properly controlled.

Studies on vesical schistosomiasis among rural Ezza farmers in the southwestern border of Ebonyi State, Nigeria.

Studies on vesical schistosomiasis and its snail vectors were carried out between October 2001-May 2002 among rural Ezza farmers inhabiting the southwestern border of Ebonyi State, Nigeria. The people are predominantly farmers. Of the 2,104 urine specimens examined in 10 communities, 466 (22.1%) comprising 305 (23.7%) men and 161 (19.7%) women were infected with visible haematuria as the predominant presenting symptom. Ezza people associate bloody urine with sexually transmitted diseases. There were no significant differences in the prevalence rates amongst various villages and sexes (p > 0.05). There was a gradual increase in the disease prevalence as the subjects' age increases. About 78.3% of the infected persons are aged 0-20 years. Statistical analysis revealed that the prevalence, intensity and visible haematuria were significantly more ( p < 0.05) in subjects under the age of 20 than subjects above 20. Among the infected population, 183 (39.3%) and 283 (60.7%) were excreting 50 eggs/10 ml urine and above 50 eggs/10 ml urine respectively. Lack of visible haematuria is a more valid indicator of the absence of vesical schistosomiasis. Of the various snails collected during malacological survey, mainly B. globosus were infected. Possible control measures are discussed.

Prevalence of Mansonella perstans infections among the nomadic Fulanis of northern Nigeria.

The study was undertaken to investigate the prevalence and clinical manifestations of Mansonella perstans infection in the nomadic Fulanis of northern Nigeria. Physical examination of 755 consenting nomads for clinical manifestations of M. perstans infection was carried out between June 1996-September 2000. This was followed by parasitological examination of blood samples collected by finger prick method to identify microfilariae (mf). Data collected was stratified by locality, age and sex, and analyzed using the Chi-square test. Overall, 66 (8.7 %) of 755 nomads were infected. Infection was higher in men (9.7 %) than in women (6.5 %) (p<0.05) and occurred in all age groups with highest prevalence in persons in the 4th (14.1 %) and 5th (17.1 %) decades of life. Fifty-six (81.8 %) of the 66 nomads with mf had clinical manifestations with periodic dizziness (18.2 %), body itching (15.2 %) was the most prevalent while back pain (7.6 %) was the least. The findings show that mansonelliasis is an important health problem in nomads. This underscores the need to establish a well-articulated Filariasis Control Programme for this group whose major health problems are rooted in their occupation and amplified by several contingencies of the environment.

Ecology of mosquitoes of Midwestern Nigeria.

BACKGROUND & OBJECTIVES: The ecology and distribution of various mosquito species is important in the determination of mosquito vector abundance and associated diseases prevalence. The distribution of various mosquito genera in natural and artificial habitats and their relative species abundance was studied between August 2002 and July 2003 in three foci (Uromi, Ekpoma and Auchi) comprising the Esan and Etsako regions of Midwestern Nigeria. METHODS: Sampling was carried out by the method of Hopkins (1952) by dipping using a pipette or ladle depending on container types. Pooled contents of smaller containers were sampled with a pond net. All breeding sources of mosquito larvae were grouped into five (5) depending on their nature, constitution and the physiochemical properties. Artificial mosquito cultures were also carried out in four different container types; plastics, metal cans, earthenware pots and bamboo strips, in parts of two different macro habitats subdivided into area of high human activities (AHHA) and areas of derived/secondary vegetation (ADSV). Environmental temperatures, rainfall and relative humidity were monitored during the study. RESULTS: The present study revealed 17 mosquito species belonging to three genera (Anopheles, Culex and Aedes) which are potential vectors of four human diseases in the areas surveyed. A total of 736 mosquito larvae were encountered in artificial sources and 568 larvae were harvested from natural sources. Pools, plastics and metal cans were the predominant artificial sources of mosquito larvae. CONCLUSION: The contribution of human activities and increasing environmental modification to the breeding of human disease vector mosquitoes is of importance and selective vector control measures including larviciding are recommended particularly before onset of rainy season.

Lymphatic filariasis among the Ezza people of Ebonyi State, eastern Nigeria.

A total of 1,243 Ezza people living in 10 communities of Ebonyi State, eastern Nigeria were examined between July 2002-January 2003 for lymphatic filariasis. This is the first time a filariasis survey due to Wuchereria bancrofti has been carried out in this state. Of the 1,243 persons examined, 210 (16.9 %) had W. bancrofti microfilariae. Infection varied significantly among communities and ages (p < 0.05) but not sex-related (p > 0.05). The Ezza people are predominantly farmers and professional hired labourers. There was a close association between microfilaria rate and microfilaria -density in various age groups (r = 0.812; p < 0.01). Microfilaria density is an important measure in the epidemiology, treatment and control of human filarisis in this endemic foci. Clinical signs and symptoms of the disease include elephantiasis, hydrocoele, dermatitis and periodic fever. Clinical symptoms without microfilaraemia and microfilaraemia without clinical symptoms were also observed. Of 1,603 mosquitoes dissected, Anopheles gambiae, An. funestus and Culex quinquefasciatus showed infectivity rates of 6.3 %, 5.1 % and 6.0 % respectively. The affected persons and other key informants are unaware of the cause of the disease and attributed it to witchcraft, violation of taboo, bad water and food. Intervention strategies to be integrated into the on-going Community-Directed Treatment with Ivermectin (CDTI) project are discussed.

Prevalence of parasitic diseases among nomadic Fulanis of south-eastern Nigeria.

A study was carried out to determine the prevalence of parasitic infections among the nomadic Fulanis of south-eastern Nigeria between September 2003-March 2004. Urine, stool and blood specimens were collected from each of 231 subjects. Of these, 98 (42.4%) were infected with one or more of 14 parasitic species, of which Plasmodium malariae had the highest prevalence (15.3%). Others included 6 intestinal helminth parasites: Ascaris lumbricoides, hookworm, Strongyloides stercoralis, Schistosoma mansoni, Enterobius vermicularis, Trichocephalus trichiurus, 2 protozoan parasites: Entamoeba histolytica and E. coli, 4 blood parasites: Mansonella perstans, Loa loa, Trypanosoma sp, Plasmodium falciparum, as well as Schistosoma haematobium recovered in the urine. Prevalence of these parasitic infections varied significantly among bush encampments, sexes, and age groups. They had evidence of onchocerciasis. Their occupational imperatives, beliefs and general life style are contributing factors to the prevalence of parasitic infections among the nomadic Fulanis of south eastern Nigeria. Aspects of prevalence and control of parasitic infections are discussed.

Control of endemic dracunculiasis in Ebonyi state, south-eastern Nigeria.

A field study was carried out in Ozibo and the Ebonyi local government area of Ebonyi state, south-eastern Nigeria to determine the effectiveness of several intervention strategies in the control of endemic dracunculiasis in that area. During the initial study prior to the application of such measures, 14,421 subjects were examined. A total of 8,688 (60.2%) persons had either Dracunculus ulcers or emergent worms. Sex-related prevalence rates were 56.1% and 63.9% for males and females respectively. Age specific prevalence rates increased with age in males, whereas highest infection rates were found in females younger than 20 years. Twenty-eight months after the introduction of intervention strategies the prevalence rate fell by 85.1% to 9% (males: by 88.2% to 6.6%, females: by 83.0% to 10.8%). Reduction rates of more than 90% were observed in males aged 10 to 19 and in females aged 0 to 9 years. Intervention measures included systematic pond treatment, distribution or replacement of filters, intensive health education, provision of hand-dug wells, regular bore-hole installation/rehabilitation as well as active case detection, containment, management, and prompt reporting. Active involvement of the endemic communities, governments and the Global 2000 staff regarding the control efforts is a necessity towards the final eradication of the disease in the near future. The relationship between some of these intervention strategies and community development are highlighted.

Endemicity of vesical schistosomiasis in the Ebonyi Benue river valley, south eastern Nigeria.

The investigation on the prevalence of patent and clinically severe infections with Schistosoma haematobium was carried out amongst inhabitants of Ebonyi Benue river valley, South Eastern Nigeria between August 2000 and June 2001. The inhabitants are predominantly farmers. Of the 3296 subjects examined from 15 randomly selected villages in the valley, 776 (23.5%) were excreting the eggs of S. haematobium in their urine. Infection rates varied between 18.9% and 30.6%. The severity of infection calculated by arithmetic mean egg counts (AMEC) and geometric mean egg counts (GMEC) varied significantly between the age groups and the villages (P < 0.05). The prevalence and severity of infection increased with age from 0 to 25 years and decreased thereafter. Symptoms associated with the disease include visible hematuria (63.1%), suprapubic pain (10.3%) and stranguary (9.9%). While 65 positive persons had more than one symptom, 64 of the positive persons had no noticeable symptoms. Visible hematuria showed moderate sensitivity and high specificity for the disease. Female genital schistosomiasis (FGS) of the lower reproductive tract was recorded in 19 females of child bearing age that complained of severe suprapubic pain. Eight snail species were recorded in the stagnant ponds and both Bulinus globosus and B. truncatus were infected with schistosome cercariae. The factors contributing to these observations and feasible control measures are discussed.

Dracunculiasis in the north eastern border of Ebonyi State, south eastern Nigeria.

Between January and August 2000, a house-to-house survey of dracunculiasis was conducted in 15 communities along the north eastern border of Ebonyi State, south eastern Nigeria. Of the 3,777 subjects examined, 192 (5.1%) had active cases of guinea worm comprising 109 males (5.5%) and 83 females (4.6%). Infections were observed in all age groups. Of the 3,777 persons examined, 2,092 (55.4%) had ever been infected in the area. Protruding adult female Dracunculus medinensis worms were found predominantly on the lower limbs (80.2%), but also on the scrotum (9.4%), umbilicus (3.1%) groin (2.6%), buttocks (20.8%) and chest (1.6%). Prevalence of dracunculiasis had no significant sex, age and occupation related differences (P > 0.1). All the 47 stagnant ponds in the area were infested with cyclops while the 6 streams and 13 newly constructed community wells were free of cyclops. Of the five species of cyclopoid copepods found in the stagnant ponds, only Thermocyclops oblongatus nigerianus and Mesocyclops aequatorialis harboured guinea worm larvae. The efforts of the endemic communities, government and international organizations in guinea worm eradication in these areas are discussed.