Impact of Mass Drug Administration (MDA) on the Transmission of Lymphatic Filariasis in Tono Irrigation Area in Navrongo, Ghana

Lymphatic filariasis is ranked as one of the leading causes of permanent and long-term disability and also oldest and most debilitating neglected tropical disease worldwide. Filariasis is caused by nematode endoparasitic worms transmitted to humans by various mosquito vectors.  World Health Organization established Global Programme to Eliminate Lymphatic Filariasis as a public health problem by the year 2020. The strategies employed are to interrupt transmission through mass drug administration (MDA) and to alleviate suffering and disability via morbidity management; and vector control. It is expected that after implementation of the strategies above, transmission assessment surveys are required to ascertain their progress, impact and efficacies. As MDA was the main strategy, this work therefore determined impact of mass drug administration on the transmission of lymphatic filariasis in Tono Irrigation area in Navrongo following more than nine years of its implementation. Human landing and pyrethrum spray monthly collections of mosquitoes in Wuru and Saboro were dissected to determine the transmission level in the study area. The mosquitoes collected in the study comprised 90.22% (3,650) Anopheles species and 9.78% (386) Culex species with no Aedes or Mansonis species. The man biting rate computed from (Human Landing Catch) HLC was 162.25 bites/man/night in Wuru and 143.75bites/man/night in Saboro. Only 3An. species were infected with filarial parasites; 2 in Saboro with 2mf, and 1L2 in a mosquito in Wuru. However, there was no L3 stage recorded in any of the 3,560 mosquitoes macerated implying that there was no ongoing transmission of LF in the study sites since no infective bites were encountered. However, a follow up survey is required to assess the level of transmission since one survey is inadequate to declare the place free of LF. Keywords: Anopheles species, Wuchereria bancrofti, Mass Drug Administration, Lymphatic filariasis, Ghan

Risk of transmission of viral haemorrhagic fevers and the insecticide susceptibility status of aedes aegypti (linnaeus) in some sites in Accra, Ghana

Background: Dengue is one of the emerging diseases that can mostly only be controlled by vector control since there is no vaccine for the disease. Although, Dengue has not been reported in Ghana, movement of people from neighbouring countries where the disease has been reported can facilitate transmission of the disease. Objective: This study was carried on the University of Ghana campus to determine the risk of transmission of viral haemorrhagic fevers and the insecticide susceptibility status of Ae. aegypti in some sites in Accra, Ghana. Design: Larval surveys were carried to inspect containers within households and estimate larval indices and adult Aedes mosquitoes were collected using human landing collection technique. WHO tube assays was used to assess the insecticide susceptibility status of Aedes mosquitoes. Results: Ae. aegypti were the most prevalent species, 75.5% and followed by Ae. vittatus, 23.9 %. Ae. albopictus and Ae. granti were in smaller numbers. Household index (HI), Breteau index (BI), and container index were calculated as 8.2%, 11.2% and 10.3% respectively with man-vector contact rate of 0.67 bites/man-hour estimated for the area. The mortalities recorded for Ae. aegypti from WHO tube assays was 88%, 94%, 80% and 99% for DDT (4%), deltamethrin (0.05%), lambdacyhalothrin (0.05%) and permethrin (0.75%) respectively.Conclusion: The survey results indicated that the density of Aedes mosquitoes was considered to be sufficient to promote an outbreak of viral haemorrhagic fevers on Legon Campus. Aedes mosquitoes were found to be resistant to DDT, deltamethrin and lamdacyhalothrin, but susceptible to permethrin. Funding: This study was supported in part by Japan Initiative for Global Research Network on Infectious Diseases(J-Grid).Keywords: Mosquitoes, Aedes aegypti, insecticide, risk, VHF transmission, Ghan

Serological evidence of vector and parasite exposure in Southern Ghana: the dynamics of malaria transmission intensity.

BACKGROUND: Seroepidemiology provides robust estimates for tracking malaria transmission when intensity is low and useful when there is no baseline entomological data. Serological evidence of exposure to malaria vectors and parasite contribute to our understanding of the risk of pathogen transmission, and facilitates implementation of targeted interventions. Ab to Anopheles gambiae salivary peptide (gSG6-P1) and merozoite surface protein one (MSP-1(19)) reflect human exposure to malaria vectors and parasites. This study estimated malaria transmission dynamics using serological evidence of vector and parasite exposure in southern Ghana. METHODS: Total IgG responses to both antigens in an age stratified cohort (14) were measured from South-eastern Ghana. 295 randomly selected sera were analyzed from archived samples belonging to a cohort study that were followed at 3 consecutive survey months (n = 885); February, May and August 2009. Temporal variations in seroprevalence of both antigens as well as differences between the age-stratified cohorts were determined by χ (2) test with p < 0.05 statistically significant. Non-parametric repeated ANOVA - Friedman's test was used to test differences in antibody levels. Seroprevalence data were fitted to reversible catalytic model to estimate sero-conversion rates. RESULTS: Whereas parasite prevalence was generally low 2.4%, 2.7% and 2.4% with no apparent trends with season, seroprevalence to both gSG6-P1 and MSP1(19) were high (59%, 50.9%, 52.2%) and 57.6%, 52.3% and 43.6% in respective order from Feb. to August. Repeated measures ANOVA showed differences in median antibody levels across surveys with specific significant differences between February and May but not August by post hoc Dunn's multiple comparison tests for gSG6-P1. For MSP1(19), no differences were observed in antibody levels between February and May but a significant decline was observed from May to August. Seroconversion rates for gSG6-P1 increased by 1.5 folds from February to August and 3 folds for MSP1(19). CONCLUSION: Data suggests exposure to infectious bites may be declining whereas mosquito bites remains high. Sustained malaria control efforts and surveillance are needed to drive malaria further down and to prevent catastrophic rebound. Operational factors for scaling up have been discussed

Indoor residual spraying with a non-pyrethroid insecticide reduces the reservoir of <i>Plasmodium falciparum</i> in a high-transmission area in northern Ghana

High-malaria burden countries in sub-Saharan Africa are shifting from malaria control towards elimination. Hence, there is need to gain a contemporary understanding of how indoor residual spraying (IRS) with non-pyrethroid insecticides when combined with long-lasting insecticidal nets (LLINs) impregnated with pyrethroid insecticides, contribute to the efforts of National Malaria Control Programmes to interrupt transmission and reduce the reservoir of Plasmodium falciparum infections across all ages. Using an interrupted time-series study design, four age-stratified malariometric surveys, each of ~2,000 participants, were undertaken pre- and post-IRS in Bongo District, Ghana. Following the application of three-rounds of IRS, P. falciparum transmission intensity declined, as measured by a >90% reduction in the monthly entomological inoculation rate. This decline was accompanied by reductions in parasitological parameters, with participants of all ages being significantly less likely to harbor P. falciparum infections at the end of the wet season post-IRS (aOR = 0.22 [95% CI: 0.19–0.26], p-value < 0.001). In addition, multiplicity of infection (MOIvar) was measured using a parasite fingerprinting tool, designed to capture within-host genome diversity. At the end of the wet season post-IRS, the prevalence of multi-genome infections declined from 75.6% to 54.1%. This study demonstrates that in areas characterized by high seasonal malaria transmission, IRS in combination with LLINs can significantly reduce the reservoir of P. falciparum infection. Nonetheless despite this success, 41.6% of the population, especially older children and adolescents, still harboured multi-genome infections. Given the persistence of this diverse reservoir across all ages, these data highlight the importance of sustaining vector control in combination with targeted chemotherapy to move high-transmission settings towards pre-elimination. This study also points to the benefits of molecular surveillance to ensure that incremental achievements are not lost and that the goals advocated for in the WHO’s High Burden to High Impact strategy are realized

Building the capacity of West African countries in Aedes surveillance: inaugural meeting of the West African Aedes Surveillance Network (WAASuN)

Arboviral diseases such as dengue, Zika and chikungunya transmitted by Aedes mosquitoes have been reported in 34 African countries. Available data indicate that in recent years there have been dengue and chikungunya outbreaks in the West Africa subregion, in countries including Côte d’Ivoire, Burkina Faso, Gabon, Senegal, and Benin. These viral diseases are causing an increased public health burden, which impedes poverty reduction and sustainable development. Aedes surveillance and control capacity, which are key to reducing the prevalence of arboviral infections, need to be strengthened in West Africa, to provide information essential for the formulation of effective vector control strategies and the prediction of arboviral disease outbreaks. In line with these objectives, the West African Aedes Surveillance Network (WAASuN) was created in 2017 at a meeting held in Sierra Leone comprising African scientists working on Aedes mosquitoes. This manuscript describes the proceedings and discusses key highlights of the meeting

<it>Mansonia africana</it> and <it>Mansonia uniformis</it> are Vectors in the transmission of <it>Wuchereria bancrofti</it> lymphatic filariasis in Ghana

<p>Abstract</p> <p>Background</p> <p>Recent data from Ghana indicates that after seven rounds of annual mass drug administration (MDA) there is still sustained transmission albeit at low levels in certain areas where <it>Anopheles melas</it>, <it>An. gambiae</it> s.s., <it>Mansonia</it> and <it>Culex</it> species are the main biting mosquitoes. <it>Anopheles gambiae</it> s.l. and <it>An. funestus</it> are the known vectors in Ghana and a recent report indicated that <it>An. melas</it> could transmit at low level microfilaraemia. However, because <it>An. melas</it> is not found everywhere there was the need to determine whether any of the other culicine species could also be playing a role in the transmission of LF.</p> <p>Methods</p> <p>Indoor mosquitoes collected once a month for three months using pyrethrum spray catches in six communities within the Kommenda-Edina-Eguafo-Abirem (KEEA) District, Central Region of Ghana were morphologically identified, dissected and examined for the presence of <it>W. bancrofti</it>. Additionally, stored mosquito samples collected during previous years in 8 communities from the Gomoa District also in the Central Region were similarly processed. The identities of all <it>W. bancrofti</it> parasites found were confirmed using an established PCR method.</p> <p>Results</p> <p>A total of 825 indoor resting mosquitoes comprising of 501 <it>Anopheles</it> species, 239 <it>Mansonia</it> species, 84 <it>Culex</it> species and 1 <it>Aedes</it> species were dissected and examined for the presence of <it>W. bancrofti</it>. <it>Mansonia africana</it> had infection and infectivity rates of 2.5<it>%</it>. and 2.1% respectively. <it>Anopheles gambiae</it> s.l. had an infection rate of 0.4% and a similar infectivity rate. None of the <it>Culex</it> sp. and <it>Aedes</it> sp were found with infection. From the stored mosquitoes the infection and infectivity rates for <it>M. africana</it> were 7.6% (N = 144) and 2.8% respectively whilst the corresponding rates for <it>M. uniformis</it> were 2.9% (N = 244) and 0.8%.</p> <p>Conclusions</p> <p>This is the first report of <it>Mansonia</it> species as vectors of lymphatic filariasis (LF) in Ghana and in West Africa since that of 1958 in Guinea. The revelation of a hitherto unrecognised vector which is possibly more efficient in transmission than the recognised ones has a profound implication for elimination of lymphatic filariasis programmes in the sub-region.</p