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Impact of repeated annual community directed treatment with ivermectin on loiasis parasitological indicators in Cameroon: Implications for onchocerciasis and lymphatic filariasis elimination in areas co-endemic with Loa loa in Africa.

ABSTRACT: BACKGROUND:Loiasis is a filarial infection endemic in the rainforest zone of west and central Africa particularly in Cameroon, Gabon, Republic of Congo, and Democratic Republic of the Congo. Repeated treatments with ivermectin have been delivered using the annual community directed treatment with ivermectin (CDTI) approach for several years to control onchocerciasis in some Loa loa-Onchocerca volvulus co-endemic areas. The impact of CDTI on loiasis parasitological indicators is not known. We, therefore, designed this cross sectional study to explore the effects of several rounds of CDTI on parasitological indicators of loiasis. METHODOLOGY/PRINCIPAL FINDINGS:The study was conducted in the East, Northwest and Southwest 2 CDTI projects of Cameroon. Individuals who consented to participate were interviewed for ivermectin treatment history and enrolled for parasitological screening using thick smears. Ivermectin treatment history was correlated with loiasis prevalence/intensity. A total of 3,684 individuals were recruited from 36 communities of the 3 CDTI projects and 900 individuals from 9 villages in a non-CDTI district. In the East, loiasis prevalence was 29.3% (range = 24.2%-34.6%) in the non-CDTI district but 16.0% (3.3%-26.6%) in the CDTI district with 10 ivermectin rounds (there were no baseline data for the latter). In the Northwest and Southwest 2 districts, reductions from 30.5% to 17.9% (after 9 ivermectin rounds) but from 8.1% to 7.8% (not significantly different after 14 rounds) were registered post CDTI, respectively. Similar trends in infection intensity were observed in all sites. There was a negative relationship between adherence to ivermectin treatment and prevalence/intensity of infection in all sites. None of the children (aged 10-14 years) examined in the East CDTI project harboured high (8,000-30,000 mf/ml) or very high (>30,000 mf/ml) microfilarial loads. Individuals who had taken >5 ivermectin treatments were 2.1 times more likely to present with no microfilaraemia than those with less treatments. CONCLUSION:In areas where onchocerciasis and loiasis are co-endemic, CDTI reduces the number of, and microfilaraemia in L. loa-infected individuals, and this, in turn, will help to prevent non-neurological and neurological complications post-ivermectin treatment among CDTI adherents.

SUBMITTER: Wanji S

PROVIDER: S-EPMC6161907 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Impact of repeated annual community directed treatment with ivermectin on loiasis parasitological indicators in Cameroon: Implications for onchocerciasis and lymphatic filariasis elimination in areas co-endemic with Loa loa in Africa.

Wanji Samuel S Chounna Ndongmo Winston Patrick WP Fombad Fanny Fri FF Kengne-Ouafo Jonas Arnaud JA Njouendou Abdel Jelil AJ Longang Tchounkeu Yolande Flore YF Koudou Benjamin B Bockarie Moses M Fobi Grace G Roungou Jean Baptiste JB Enyong Peter A PA

PLoS neglected tropical diseases 20180918 9

<h4>Background</h4>Loiasis is a filarial infection endemic in the rainforest zone of west and central Africa particularly in Cameroon, Gabon, Republic of Congo, and Democratic Republic of the Congo. Repeated treatments with ivermectin have been delivered using the annual community directed treatment with ivermectin (CDTI) approach for several years to control onchocerciasis in some Loa loa-Onchocerca volvulus co-endemic areas. The impact of CDTI on loiasis parasitological indicators is not known ...[more]

PMID: 30226900

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Project description:BackgroundLoiasis is a filarial disease caused Loa loa. The main vectors are Chrysops silacea and C. dimidiata which are confined to the tropical rainforests of Central and West Africa. Loiasis is a mild disease, but individuals with high microfilaria loads may suffer from severe adverse events if treated with ivermectin during mass drug administration campaigns for the elimination of lymphatic filariasis and onchocerciasis. This poses significant challenges for elimination programmes and alternative interventions are required in L. loa co-endemic areas. The control of Chrysops has not been considered as a viable cost-effective intervention; we reviewed the current knowledge of Chrysops vectors to assess the potential for control as well as identified areas for future research.ResultsWe identified 89 primary published documents on the two main L. loa vectors C. silacea and C dimidiata. These were collated into a database summarising the publication, field and laboratory procedures, species distributions, ecology, habitats and methods of vector control. The majority of articles were from the 1950-1960s. Field studies conducted in Cameroon, Democratic Republic of Congo, Equatorial Guinea, Nigeria and Sudan highlighted that C. silacea is the most important and widespread vector. This species breeds in muddy streams or swampy areas of forests or plantations, descends from forest canopies to feed on humans during the day, is more readily adapted to human dwellings and attracted to wood fires. Main vector targeted measures proposed to impact on L. loa transmission included personal repellents, household screening, indoor residual spraying, community-based environmental management, adulticiding and larviciding.ConclusionsThis is the first comprehensive review of the major L. loa vectors for several decades. It highlights key vector transmission characteristics that may be targeted for vector control providing insights into the potential for integrated vector management, with multiple diseases being targeted simultaneously, with shared human and financial resources and multiple impact. Integrated vector management programmes for filarial infections, especially in low transmission areas of onchocerciasis, require innovative approaches and alternative strategies if the elimination targets established by the World Health Organization are to be achieved.

Project description:BackgroundLymphatic filariasis (LF) is among the 10 neglected tropical diseases targeted for control or elimination by 2020. For LF elimination, the World Health Organization (WHO) has proposed a comprehensive strategy including (i) interruption of LF transmission through large-scale annual treatment (or mass drug administration (MDA)) of all eligible individuals in endemic areas, and (ii) alleviation of LF-associated suffering through morbidity management and disability prevention. In Cameroon, once-yearly mass administration of ivermectin and albendazole has been implemented since 2008. The aim of this study was to assess progress towards the elimination goal, looking specifically at the impact of six rounds of MDA on LF transmission in northern Cameroon.MethodologyThe study was conducted in the North and Far North Regions of Cameroon. Five health districts that successfully completed six rounds of MDA (defined as achieving a treatment coverage ≥ 65% each year) and reported no positive results for Wuchereria bancrofti microfilariaemia during routine surveys following the fifth MDA were grouped into three evaluation units (EU) according to WHO criteria. LF transmission was assessed through a community-based transmission assessment survey (TAS) using an immunochromatographic test (ICT) for the detection of circulating filarial antigen (CFA) in children aged 5-8 years old.Principal findingsA total of 5292 children (male/female ratio 1.04) aged 5-8 years old were examined in 97 communities. Positive CFA results were observed in 2, 8 and 11 cases, with a CFA prevalence of 0.13% (95% CI: 0.04-0.46) in EU#1, 0.57% (95% CI: 0.32-1.02) in EU#2, and 0.45% (95% CI: 0.23-0.89) in EU#3.Conclusion/significanceThe positive CFA cases were below WHO defined critical cut-off thresholds for stopping treatment and suggest that transmission can no longer be sustained. Post-MDA surveillance activities should be organized to evaluate whether recrudescence can occur.

Project description:BackgroundLoiasis, a filarial infection caused by Loa loa usually thought to cause relatively minor morbidity, can cause serious and often fatal reactions in patients carrying very high levels of circulating Loa loa microfilariae (mf) following administration of microfilaricidal drugs. An experimental model of this condition would greatly aid the definition of the optimal management of this important clinical presentation.Methodology/principle findingsFifteen baboons (Papio anubis) were infected with 600 infective larvae (L3) isolated from Chrysops vector flies. Animals were observed for any clinical changes; blood samples were collected every 1-2 months for 22 months, and analysed for parasitological, hematological and biochemical profiles using standard techniques. All animals became patent but remained clinically normal throughout the study. The parasitological pre-patent period was between 4-8 months, with a majority (60%) of animals becoming patent by 5 months post infection (MPI); all animals were patent by 8 MPI. Microfilarial loads increased steadily in all animals and reached a peak at 18 MPI. By 10 MPI >70% of animals had mf >8,000 mf/mL, and at 18 MPI >70% of animals had mf >30,000 mf/mL with 50% of these animals with mf >50,000 mf/mL. Absolute eosinophil, creatinine, Ca2+ and K+ levels were generally above normal values (NV). Positive associations were seen between microfilariaemia and eosinophilia, Hb, Ca2+, and gamma-GT values, whilst significant negative associations were seen between microfilariaemia and potassium, glucose and mononuclear leukocyte levels.ConclusionsInfection of splenectomised baboons with L. loa can induce levels of circulating microfilariae, and corresponding haematological profiles, which parallel those seen in those humans in danger of the severe post-microfilariacide clinical responses. Utilization of this experimental model could contribute to the improved management of the loiasis related adverse responses in humans.

Project description:In Burkina Faso, onchocerciasis was no longer a public health problem when the WHO Onchocerciasis Control Programme in West Africa closed at the end in 2002. However, epidemiological surveillance carried out from November 2010 to February of 2011, showed a recrudescence of infection in the Cascades Region. This finding was made at a time when ivermectin, a drug recommended for the treatment of both onchocerciasis and lymphatic filariasis, had been distributed in this area since 2004 for the elimination of lymphatic filariasis. It was surprising that ivermectin distributed for treating lymphatic filariasis had not prevented the recrudescence of onchocerciasis. Faced with this situation, the aim of our study was to evaluate the effectiveness of ivermectin on the onchocerciasis parasite. The percentage reduction in microfilarial load after treatment with ivermectin was used as a proxy measure for assessing possible resistance. A cohort study was carried out with 130 individuals who had tested positive for microfilariae of Onchocerca volvulus in 2010 using microscopic examination of skin-snip biopsies from five endemic villages. Subjects were followed from July 2011 to June 2012. The microfilarial load of each individual was enumerated by skin-snip biopsy in 2010, prior to the first ivermectin treatment against onchocerciasis under community guidelines. All individuals received two ivermectin treatments six months apart. In 2012, the microfilarial loads were determined again, six months after the second round of ivermectin and the reductions in parasite loads were calculated to measure the impact of the drug. The percentage reduction of the microfilarial loads ranged from 87% to 98% in the villages. In all villages, there was a statistically significant difference between the average microfilarial loads in 2010 and 2012. The level of reduction of microfilarial loads suggests that ivermectin is effective against the recrudescent population of O. volvulus in Cascades Region of Burkina Faso. Further investigations would be necessary to determine the causes of the recrudescence of onchocerciasis. (For French language abstract, see S1 Alternative Language Abstract-Translation of the Abstract into French by the authors.).

Dataset Information

Impact of repeated annual community directed treatment with ivermectin on loiasis parasitological indicators in Cameroon: Implications for onchocerciasis and lymphatic filariasis elimination in areas co-endemic with Loa loa in Africa.

Publications

Impact of repeated annual community directed treatment with ivermectin on loiasis parasitological indicators in Cameroon: Implications for onchocerciasis and lymphatic filariasis elimination in areas co-endemic with Loa loa in Africa.

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