Population dynamics of Onchocerca volvulus microfilariae in human host after six years of drug control

Background & objectives: Mass administration of ivermectin drug was carried out annually between 1995 and 2001 in three villages that were endemic for onchocerciasis in the Lower Cross River Basin, Nigeria. The aim of this study was to evaluate the population dynamics (dispersion patterns, distribution, prevalence and intensity) of Onchocerca volvulus microfilariae in their human host after six years of ivermectin treatment. Methods: A total of 1014 subjects from three rural areas in Etung Local Government Area of Cross River State, Nigeria were screened for skin microfilariae using standard parasitological method of diagnosis. Results: Ivermectin drug intervention had significantly reduced the prevalence of skin microfilariae (PMF) from 69.3% pre-control to 39.3% and community microfilarial load (CMFL) from 7.11 to 2.31 microfilariae per skin snip. Males (45%) were significantly (p <0.05) more infected than females (34%). Both microfilarial prevalence and intensity increased with age. Pearson correlation test between intensity and age was not significant (r = 0.37; p >0.05). The correlation between age-dependent parasite prevalence and mean abundance was also not significant (r = 0.42; p >0.05). The degree of dispersion as measured by variance to mean ratio (VMR), coefficient of variation (CV) and exponent ‘K’ of the negative binomial model of distribution showed that the parasite aggregated, clumped and overdispersed in their human host. The relative index of potential infection of each age group showed that adults between the age of 21 and 50 yr accounted for 52.7% of microfilariae positive cases. Interpretation & conclusion: Aggregated and overdispersion of O. volvulus observed in this study showed that active transmission could still be going on, because the tendency of the vector, Simulium damnosum ingesting more microfilariae was high due to the aggregated and overdispersed nature of the parasite with its host

Morphological and molecular characterization of endophilic Anopheles gambiae complex, in Itu Local Government Area, Akwa Ibom State, Nigeria

Malaria is still regarded as a major public health problem in sub-Saharan African countries. Anopheles mosquitoes have been implicated as the major malaria vectors. However, species abundance, composition and distribution vary between different ecological zones. This study investigated the composition and distribution of Anopheles gambiae mosquitoes in Itu Local Government Area, Akwa Ibom State, Nigeria. Adult Anopheles mosquitoes were sampled bi-weekly from 15 randomly selected houses each from three communities in the study area by pyrethroid spray capture (PSC) method. Adult Anopheles species were identified morphologically and sibling species were further subjected to species- specific polymerase chain reaction (PCR) typing. A total of 269 female Anopheles species were caught between July and December, 2015. The study indicated significant (p&lt;0.05) abundance of Anopheles gambiae siblings, with An. gambiae s.s recording 219(81.41%) followed by An. arabiensis 32(11.90%). A proportion of the samples were unidentified 18(6.69%). There was a significant difference (p&lt;0.05) in the distribution of A. gambiae complex over the period of the study with a peak in September 89(33.01%). Anopheles mosquitoes were more abundant in Itu Oma 120(44.66%) than West Itam 98(36.43%) and East Itam 51(18.96%). The study also recorded significantly (p&lt;0.05) higher rate of blood engorged female Anopheles (54.05%). This finding showed that An. gambiae s.s was the predominant malaria vector in the area and also, the incidence of malaria been likely to increase during the wet season. Therefore, vector control must be carried out in these communities to reduce the number of these indoor biting mosquitoes. This study therefore, will be useful as baseline data to help design strategies for malaria control in Itu Local Government Area and also facilitate the success of the ongoing effort on the malaria control programme in the State. Keywords: Malaria; Anopheles, morphological; molecular; characterization; Akwa Ibom; Nigeria

Qualitative biagnosis of urinary schistosomiasis in two endemic communities of Rross River Basin

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Urinary Schistosomiasis in Two Endemic Communities of Cross River Basin: Prevalence, Intensity, and Treatment

We diagnosed schistosomiasis due to S. haematobium in Obudu and Biase Local Government Areas of Cross River State, Nigeria, using the membrane filtration technique. Altogether, 1,326 urine samples where screened. Of the 722 individual urine screened in Biase, 444 (61.5%) were positive cases, while in Obudu 354 (58.6%) were positive out of the 604 subjects screened. Males from both communities had a higher prevalence and intensity rate (P< 0.05) than Females. The relative index of potential infection (RIPI) of each age group shows that 6-20 yeas of age contributed 84.22% and 87.4% of total contamination of the environment with S. haematobium eggs in Biase and Obudu respectively. Treatment with praziquantel (40mgkg-1) of 80 randomly selected positive cases from both communities showed a cure rate of 57.1-100% at 7-56 days after treatment. Key Words: Schistosoma haematobium, Cross River Basin, Prevalence, Intensity, Praziquantel. [Mary Slessor Jnl of Medicine Vol.3(1) 2003: 28-34

Susceptibility of Anopheles gambiae complex to carbamates and organophosphate insecticides in Uyo, Akwa Ibom State, Nigeria

Rapid emergence in insecticide resistance among malaria vector populations to commonly used public health insecticides poses a challenge to current malaria vector control strategies and interventions in sub- Saharan Africa. This study was conducted to determine the susceptibility status of female An.gambiae s.l to Propoxur (0.01%) and bendiocarb (0.1%) (carbamate) and pirimiphosmethyl (0.25%) (organophosphate) insecticides in Uyo Metropolis, Akwa Ibom State, Nigeria. The larvae of An. gambiae s.l were collected from natural water bodies and other potential breeding sites from different sites in Uyo Metropolis. Insecticide susceptibility bioassays were performed according to the World Health Organization standard operating procedures on 2-3 days old, sugar-fed but none blood fed female Anopheles mosquitoes. Post exposure mortality after 24 hours and knockdown values for KDT50 and KDT95 were calculated. Knock-down at 1 hour insecticide exposure ranged from 94 % to 100 %. Mortality after 24 hours post exposure was 100% for all insecticides except Propoxur which was 98 %. There was high variability in KDT50 and KDT95 values (in minutes) with propoxur (4.337 and 15.620), Bendiocarb (9.523 and 20.996) and pirimiphosmethyl (39.908 and 61.722) respectively. Adopting the WHO criteria, the mosquitoes were not resistant to any of the insecticides tested. The results therefore showed that vector control campaigns employing the use of any of these insecticides in the study area would not be compromised. However, there is need for continued monitoring to ensure early detection of resistance. Keywords: Anopheles gambiae; insecticide susceptibility; Uyo; Akwa Ibom State; Nigeria