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Relationship between oral declaration on adherence to ivermectin treatment and parasitological indicators of onchocerciasis in an area of persistent transmission despite a decade of mass drug administration in Cameroon.

Wanji S, Kengne-Ouafo JA, Esum ME, Chounna PW, Adzemye BF, Eyong JE, Jato I, Datchoua-Poutcheu FR, Abong RA, Enyong P, Taylor DW - Parasit Vectors (2015)

Bottom Line: There was a treatment-dependent reduction in microfilaria prevalence (rs =-0.986, P = 0.01) and intensity (rs =-0.96, P = 0.01).The highest mf prevalence (59.7%) was found in the zero treatment group and the lowest (33.9%) in the ≥ 7 times treatment group (OR = 2.8; 95% CI [2.09-3.74]; P < 0.001).Our findings show that using parasitological indicators, reduction in prevalence is IVM intake-dependent and that participants' oral declaration of treatment adherence could be relied upon for impact studies.

View Article: PubMed Central - PubMed

Affiliation: Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O.Box 63, Buea, Cameroon. swanji@yahoo.fr.

ABSTRACT

Background: Onchocerciasis control for years has been based on mass drug administration (MDA) with ivermectin (IVM). Adherence to IVM repeated treatment has recently been shown to be a confounding factor for onchocerciasis elimination precisely in rain forest areas where transmission continues and Loa loa co-exists with Onchocerca volvulus. In this study, participants' oral declarations were used as proxy to determine the relationship between adherence to IVM treatment and parasitological indicators of onchocerciasis in the rain forest area of Cameroon with more than a decade of MDA.

Methods: Participants were recruited based on their IVM intake profile with the aid of a semi-structured questionnaire. Parasitological examinations (skin sniping and nodule palpation) were done on eligible candidates. Parasitological indicators were calculated and correlated to IVM intake profile.

Results: Of 2,364 people examined, 15.5% had never taken IVM. The majority (40.4%) had taken the drug 1-3 times while only 18% had taken ≥ 7 times. Mf and nodule prevalence rates were still high at 47%, 95% CI [44.9-49.0%] and 36.4%, 95% CI [34.4-38.3%] respectively. There was a treatment-dependent reduction in microfilaria prevalence (rs =-0.986, P = 0.01) and intensity (rs =-0.96, P = 0.01). The highest mf prevalence (59.7%) was found in the zero treatment group and the lowest (33.9%) in the ≥ 7 times treatment group (OR = 2.8; 95% CI [2.09-3.74]; P < 0.001). Adults with ≥ 7 times IVM intake were 2.99 times more likely to have individuals with no microfilaria compared to the zero treatment group (OR = 2.99; 95% CI [2.19-4.08], P < 0.0001). There was no clear correlation between treatment and nodule prevalence and intensity.

Conclusion: Adherence to ivermectin treatment is not adequate in this rain forest area where L. loa co-exists with O. volvulus. The prevalence and intensity of onchocerciasis remained high in individuals with zero IVM intake after more than a decade of MDA. Our findings show that using parasitological indicators, reduction in prevalence is IVM intake-dependent and that participants' oral declaration of treatment adherence could be relied upon for impact studies. The findings are discussed in the context of challenges for the elimination of onchocerciasis in this rain forest area.

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Related in: MedlinePlus

Changes in the proportion of study population in defined nodule load groups in relation to IVM intake profile. (Number of people examined per IVM intake groups: [0 time] = 367; [1-3 times] = 956; [4-6 times] =615; [≥7 times] =426). P-value given for each defined nodule load group Significance level set at 5 %
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Fig7: Changes in the proportion of study population in defined nodule load groups in relation to IVM intake profile. (Number of people examined per IVM intake groups: [0 time] = 367; [1-3 times] = 956; [4-6 times] =615; [≥7 times] =426). P-value given for each defined nodule load group Significance level set at 5 %

Mentions: No clear relationship between treatment and nodule intensity was found. Of 1,504 individuals with zero nodules, 61.9 % had never taken ivermectin. This proportion was similar for all the other IVM intake groups (P = 0.168). The same observation was made with people with nodules. For individuals with > 7 times IVM intake, 6.3 % had > 3 nodules, this proportion was not significantly different from 8.7 % that of people who had never taken IVM (P = 0.254, Fig. 7).Fig. 7


Relationship between oral declaration on adherence to ivermectin treatment and parasitological indicators of onchocerciasis in an area of persistent transmission despite a decade of mass drug administration in Cameroon.

Wanji S, Kengne-Ouafo JA, Esum ME, Chounna PW, Adzemye BF, Eyong JE, Jato I, Datchoua-Poutcheu FR, Abong RA, Enyong P, Taylor DW - Parasit Vectors (2015)

Changes in the proportion of study population in defined nodule load groups in relation to IVM intake profile. (Number of people examined per IVM intake groups: [0 time] = 367; [1-3 times] = 956; [4-6 times] =615; [≥7 times] =426). P-value given for each defined nodule load group Significance level set at 5 %
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4696282&req=5

Fig7: Changes in the proportion of study population in defined nodule load groups in relation to IVM intake profile. (Number of people examined per IVM intake groups: [0 time] = 367; [1-3 times] = 956; [4-6 times] =615; [≥7 times] =426). P-value given for each defined nodule load group Significance level set at 5 %
Mentions: No clear relationship between treatment and nodule intensity was found. Of 1,504 individuals with zero nodules, 61.9 % had never taken ivermectin. This proportion was similar for all the other IVM intake groups (P = 0.168). The same observation was made with people with nodules. For individuals with > 7 times IVM intake, 6.3 % had > 3 nodules, this proportion was not significantly different from 8.7 % that of people who had never taken IVM (P = 0.254, Fig. 7).Fig. 7

Bottom Line: There was a treatment-dependent reduction in microfilaria prevalence (rs =-0.986, P = 0.01) and intensity (rs =-0.96, P = 0.01).The highest mf prevalence (59.7%) was found in the zero treatment group and the lowest (33.9%) in the ≥ 7 times treatment group (OR = 2.8; 95% CI [2.09-3.74]; P < 0.001).Our findings show that using parasitological indicators, reduction in prevalence is IVM intake-dependent and that participants' oral declaration of treatment adherence could be relied upon for impact studies.

View Article: PubMed Central - PubMed

Affiliation: Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O.Box 63, Buea, Cameroon. swanji@yahoo.fr.

ABSTRACT

Background: Onchocerciasis control for years has been based on mass drug administration (MDA) with ivermectin (IVM). Adherence to IVM repeated treatment has recently been shown to be a confounding factor for onchocerciasis elimination precisely in rain forest areas where transmission continues and Loa loa co-exists with Onchocerca volvulus. In this study, participants' oral declarations were used as proxy to determine the relationship between adherence to IVM treatment and parasitological indicators of onchocerciasis in the rain forest area of Cameroon with more than a decade of MDA.

Methods: Participants were recruited based on their IVM intake profile with the aid of a semi-structured questionnaire. Parasitological examinations (skin sniping and nodule palpation) were done on eligible candidates. Parasitological indicators were calculated and correlated to IVM intake profile.

Results: Of 2,364 people examined, 15.5% had never taken IVM. The majority (40.4%) had taken the drug 1-3 times while only 18% had taken ≥ 7 times. Mf and nodule prevalence rates were still high at 47%, 95% CI [44.9-49.0%] and 36.4%, 95% CI [34.4-38.3%] respectively. There was a treatment-dependent reduction in microfilaria prevalence (rs =-0.986, P = 0.01) and intensity (rs =-0.96, P = 0.01). The highest mf prevalence (59.7%) was found in the zero treatment group and the lowest (33.9%) in the ≥ 7 times treatment group (OR = 2.8; 95% CI [2.09-3.74]; P < 0.001). Adults with ≥ 7 times IVM intake were 2.99 times more likely to have individuals with no microfilaria compared to the zero treatment group (OR = 2.99; 95% CI [2.19-4.08], P < 0.0001). There was no clear correlation between treatment and nodule prevalence and intensity.

Conclusion: Adherence to ivermectin treatment is not adequate in this rain forest area where L. loa co-exists with O. volvulus. The prevalence and intensity of onchocerciasis remained high in individuals with zero IVM intake after more than a decade of MDA. Our findings show that using parasitological indicators, reduction in prevalence is IVM intake-dependent and that participants' oral declaration of treatment adherence could be relied upon for impact studies. The findings are discussed in the context of challenges for the elimination of onchocerciasis in this rain forest area.

Show MeSH
Related in: MedlinePlus