Evaluation of epidemiological mapping strategies and diagnostic tool for onchocerciasis and lymphatic filariasis in hypo-endemic Amaya district, South-Western Ethiopia

doi:10.21203/rs.3.rs-3024795/v1

Onchocerciasis is a parasitic neglected tropical disease caused by a filarial nematode called Onchocerca volvulus. During the period of the onchocerciasis control program in Ethiopia, larger areas with onchocerciasis prevalence of less than 20% were classified as hypo-endemic. In 2012, the goal of the program has been shifted from control to elimination, which required the evaluation of mapping strategies and assessment of transmission status. However, there is no clear mapping strategy for onchocerciasis and lymphatic filariasis in the elimination context in these areas. Hence, the study evaluated the mapping strategies in first-line and randomly selected villages and matched school children to random villages.

Methods

A cross-sectional study involving a total of 2756 study participants; 1181 from four purposively selected first-line villages, 372 from random villages, and 1203 from matched schools children to random villages was conducted in 2019 at Amaya district South-western Shoa zone of Oromia region of Ethiopia. Approximately 175 µL finger prick blood was collected from each study participant. Oncho/LF IgG4 bi-plex rapid diagnostic test was conducted using 10 µL blood and dried blood spot were prepared using the remaining blood samples for further conformation by SD-ELISA. Data were captured using open data kit software programmed tablet, exported, and analyzed by SPSS version 23 software. The sensitivity and specificity of the Oncho/LF IgG4 bi-plex test were evaluated against SD-ELISA as the reference standard based on the manufacturer’s claims.

Results

The prevalence of onchocerciasis among first-line, randomly selected villages and matched-school children in random villages were 8.3%, 4.6%, and 0.33% respectively. The prevalence of lymphatic filariasis in first-line villages was 1.02%, while 1.1% in random villages. The co-endemicity of onchocerciasis with lymphatic filariasis was 0.42% in the first line and 1.08% in randomly selected villages. The sensitivity and specificity of the Oncho/LF IgG4 bi-plex test were 26.09 % and 99.93%.

Conclusions

The study indicated Amaya district qualifies for onchocerciasis mass drug administration threshold (>2%) average in both first-line and randomly selected villages. In both first and random villages, onchocerciasis and lymphatic filariasis were co-endemic indicating the need of integrating mapping strategies. First-line and random village-based mapping strategies are recommended for onchocerciasis in hypo-endemic areas.

Onchocerciasis

Lymphatic filariasis

Human onchocerciasis commonly named river blindness is a filarial disease caused by the parasite Oochocerca volvulus and is one of the most debilitating neglected tropical diseases (NTDs) (1). It is the major cause of visual impairment, blindness, disfiguring skin lesions, and severe itching (2).

Though large-scale elimination activities have been implemented, in 2019 WHO estimated 217.5 million people globally require mass drug administration (MDA) with ivermectin of whom the majority in Sub-Saharan Africa (3) and 218 million people were living in areas at risk of onchocerciasis transmission (4).

In Ethiopia, an Italian investigator first reported the existence of onchocerciasis in the Southwest of the country in 1939 (5). Since then, extensive epidemiological surveys conducted by numerous investigators confirmed the presence of the disease with varying degrees of endemicity in the Southwestern, Western, and Northwestern parts of the country (6). To achieve onchocerciasis elimination, the transmission status of all districts should be known to document focus-based information for countrywide dossier preparation to apply to WHO for elimination certification (7).

However, there are hypo-endemic areas in the country that remain fully unmapped, and comprehensive elimination mapping of onchocerciasis transmission might be needed to ascertain its full distribution to determine the actual numbers of persons at risk and implement an intervention in the remaining areas of the country (8).

While shifting from onchocerciasis control to elimination, defining the operational unit for elimination mapping requires an understanding of its distribution and communities that were not under treatment but the prevalence of Onchocerca volvulus infection is high enough to sustain transmission (9). During the African program of onchocerciasis control (APOC) period, hypo-endemic areas mapped by rapid epidemiological mapping of onchocerciasis (REMO) with nodule prevalence less than 20 were considered below the threshold to initiate intervention. However, in the elimination goal, defining the operational unit for MDA implementation should be reassessed to determine the level of endemicity that might sustain transmission (10). Unfortunately, neither a precise threshold nor the appropriate sampling strategies had been determined to initiate MDA in hypo-endemic areas (11).

In addition, knowing the vectors’ biology of onchocerciasis lead to thinking in terms of its transmission zones or foci. However, a more convenient operational unit for program implementation is usually a district or equivalent (9). Although all parts of a district are not equal in terms of disease transmission or treatment requirements, defining the implementation unit as a sub-district should be considered (9). Hence, identifying those districts that are completely free of disease and those that require treatment at sub-district where treatment decisions differ from the rest is essential in assessing unmapped hypo-endemic areas (12).

While shifting from control to elimination, optimized diagnostic tools for elimination mapping are required. The earlier diagnostic tools for disease control through clinical evaluation of nodules and microscopic detection of microfilariae in skin snips for the previous mapping were not sensitive enough to detect the lowest level of infection (13).

The availability of OV-16 serology either in an Enzyme-Linked Immunosorbent Assay (ELISA) or Rapid Diagnostic Test (RDT) is a more sensitive indicator of infection or exposure to infection since it detects a host’s antibody response to the parasite (14). However, the challenges remain in discriminating positive from negative responses with complete certainty, especially in populations having very low levels of infection with measurable thresholds taking into account the specificity and sensitivity of the diagnostic test available for onchocerciasis (13).

On the other hand, the target populations sampled by earlier mapping (REMO) were adult males (15). Even though positive findings in adults were definitive for identifying infection in the population, more indicative of recent transmission is children with some groups recommended for assessment guiding the decision to stop MDA (7). The earlier purposive sampling strategy to identify first and second-line villages concerning blackflies breeding sites along fast-flowing rivers remains valuable but not sufficient for elimination mapping. For instance, in countries where districts are the operational units for treatment if purposive village sampling identifies onchocerciasis, those districts could be defined as endemic and treatment could start throughout (8). However, if the initial purposive village sampling does not detect onchocerciasis, further sampling is required either additional purposive sampling in likely places or random cluster surveys broadly across the district (8). Hence, elimination mapping requires establishing a standardized sampling strategy based on the best evidence.

In elimination mapping, assessing other potentially co-endemic filarial infections with onchocerciasis transmission and overlapping co-endemic filarial infections could help in the integration of inventions for NTDs elimination(16). Therefore, it is essential to establish strategies that address onchocerciasis co-endemic lymphatic filariasis based on the best evidence (16).

Therefore, this study was conducted to generate information in defining the operational unit for elimination mapping in understanding the distribution of the infection at district and sub-district levels and to evaluate diagnostic tool (Oncho/LF IgG4 bi-plex) for elimination mapping which might be used as a point of care test to start MDA, assess the impacts and stop MDA intervention. In addition, the study was conducted to generate information in establishing a sampling strategy and defining target populations in MDA initiation, impact assessment, and stop MDA. Furthermore, the study was conducted to generate information for a coordinated mapping strategy on lymphatic filariasis and onchocerciasis that enable integrated planning for MDA and establish strategies to address these challenges.

Study design, area, population, and sampling techniques

A cross-sectional study was conducted in December 2019 in the Oromia region, Southwestern Shoa Zone, Amaya district which was previously considered hypo-endemic for onchocerciasis by rapid epidemiological mapping of onchocerciasis (REMO) strategy and was not included in ivermectin MDA.

Adults population whose age is greater than 20 years, adolescents from 10-20, and children from 5 to 9 years, were included from four purposively selected first-line villages proximal to the river systems expected to be the breeding sites for the blackflies vector of onchocerciasis.

In addition, 29 randomly selected second-line villages, and 24 matched schools to randomly selected villages independent of first-line villages were included in the study. These, adults greater than 20 years from 29 randomly selected villages, students attending grades 3 and 4 whose ages were from 10-14 years from 24 matched-schools children to randomly selected villages were provided blood samples for the study.

Blood sample collection and laboratory testing

Approximately, 175 µL of whole blood samples were collected from a finger prick in Ethylene Diamine Tetra Acetic Acid (EDTA) tube by trained laboratory professionals, and 10µl of whole blood was added via pipette to the sample pad of the Oncho/LF Ig G4 bi-plex, four drops of assay diluent were added to the diluent well and the results were interpreted at 30 minutes according to the manufacturer’s instruction. In the mean-time from each individual, approximately 60µlof whole blood was added via pipette onto Whatman filter paper for a confirmatory test by ELISA, dried at ambient temperature, preserved, and maintained at -20^oC at Ethiopian Public Health Institute (EPHI) reference laboratory.

For the SD onchocerciasis IgG4 ELISA test, the micro-assay plate was pre-coated with the Ov-16 antigen and eluted specimens were transferred to a micro-assay well. If Ov-16 antibodies are present, they bind to the immobilized antigen and upon addition conjugate, it forms an antigen/antibody complex. Following the addition of substrate, color is detected due to the enzyme-antibody-antigen complexes formed in the presence of Ov16 antigen and conjugate. Each plate was re-assessed based on absorbance data of control to determine if the plate and sample meet quality. The value of each absorbance result was compared to the control. Based on the mean absorbance of the calibrator cut-off value, the samples were categorized as negatives if their absorbance is less than the cut-off values and positive if greater than or equal to equal to the cut-off value.

Data management and analysis

Participants’ information data was collected on ODK smartphones and uploaded regularly to an electronic database at Ethiopian Public Health Institute (EPHI) server. Code numbers of personal information were linked from personal identifiers, and a single master database was maintained for data entry, cleaning, and quality assurance. SPSS version 23 was used to determine the prevalence of onchocerciasis and lymphatic filariasis. A chi-square test was employed to determine the association between the positivity rate of onchocerciasis and lymphatic filariasis with the age and sex of study participants. The sensitivity, specificity, positive predictive value, and negative predictive value of the Oncho/LF IgG4 bi-plex test were evaluated against SD ELISA as the reference standard based on the manufacturer’s claim.

Operational definitions:

Hypo-endemic: The prevalence of onchocerciasis is less than >0 and < 20 based on REMO, nodule palpation of adult males of about 30-50.

Meso-endemic: The prevalence of onchocerciasis less than >20 and <40 based on REMO, nodule palpation of adult males of about 30-50

Hyper-endemic: The prevalence of onchocerciasis is less than >40 based on rapid REMO nodule palpation of adult males of about 30-50.

First-line villages: the villages that are proximal main rivers system that is expected to be the breeding sites for black fly vectors for onchocerciasis

Socio-demography of study participants, randomly selected and matched school children

In this study, a total of 1181(573 female) were purposively included in the study from four first-line villages. However, 372, 149 (40.1%) males from randomly included in villages, and 1203 matched-school children to randomly selected second-line villages (Table 1).

Prevalence of onchocerciasis among four first-line villages

Of 1181 study participants, 98 were positive for onchocerciasis using SD ELISA. Of 98 who were positive, 64 were male. The prevalence of onchocerciasis in four first-line villages (Abuko, Quban loli, Garo, and Aroji Magala oli) was 14.43%, 2.91%, 3.48%, and 11.46% respectively. Of the four first-line villages, Abuko village has the highest prevalence (14.43%) indicated in Table 2. The overall prevalence among first-line villages was (8.3%) by SD ELISA.

Prevalence of onchocerciasis by age and sex from four first-line villages

The prevalence of onchocerciasis in first-line villages was assessed based on the results of SD ELISA to ascertain mapping strategies based on age and sex stratification. The prevalence of onchocerciasis by age categories (5-9, 10-20, and > 20 years) was 6.5%, 5.7%, and 12.9% respectively. The highest prevalence was observed in the age category of >20 (12.9%), (Table 3).

Prevalence of onchocerciasis among randomly selected villages

From 29 randomly selected villages, a total of 372, 149 (40.1%) males were enrolled in the study. The positivity rate among females was 5 (2.2%) and 12(8.1) among males. The overall prevalence of onchocerciasis was 4.6%. Out of 29 randomly selected villages, the prevalence of onchocerciasis was zero in 19(63%) of the villages (indicated in Table 4).

Prevalence of onchocerciasis among matched school children in randomly selected villages

For 29 randomly selected second-line villages, a total of 1203 matched-school children, 652 (54.2%) male, and 551 (45.8) female were tested for onchocerciasis by Oncho/LF IgG4 biplex test. Only 24 schools to 29 matched villages (some random villages have no schools or share the same school with some villages). From the total tested, 3 males (0.5%) and 1 female (0.2%) were positive for onchocerciasis indicating a 0.33% prevalence of onchocerciasis in matched-school children. Illustrated in Table 5.

Prevalence of lymphatic filariasis among first-line villages

The prevalence of lymphatic filariasis was assessed by Oncho/LF Ig G4 bi-plex test results. From 1181 study participants from four first-line villages 11(3.6%) were found positive for lymphatic filariasis in Abuko village and 1(0.3) in Aroji Magala Oli with an overall prevalence of 12(1.02% indicated in Table 6.

Prevalence of lymphatic filariasis among randomly selected villages

Of 372 study participants, only 4(2.7%) males were positive for lymphatic filariasis by the Oncho/LF IgG4 bi-plex test with the overall prevalence of lymphatic filariasis 1.1%.

Prevalence of lymphatic filariasis in matched-school children in randomly selected villages

From each randomly selected village, a total of 1203 matched-school children, 652 (54.2%) male, and 551 (45.8) female were enrolled in the study and tested for lymphatic filariasis by Oncho/LF IgG4 bi-plex test. From the total tested, 2 males (0.3%) and female 1(0.2%) were positive for lymphatic filariasis and onchocerciasis implying the endemicity of onchocerciasis and lymphatic filariasis was 0.25%.

Co-endemicity of onchocerciasis and lymphatic filariasis in first-line villages

Of 1,181 study participants for whom blood samples were taken from first-line villages, 98(8.3%) were positive for onchocerciasis using SD ELISA. However, serological tests were conducted by SD Oncho/LF IgG4 bi-plex test for lymphatic filariasis. From those tested by the SD Oncho/LF igG4 bi-plex test, 21 were positive for onchocerciasis by SD ELISA, and 5 were positive by SD Oncho/LF IgG4 bi-plex for lymphatic filariasis. The overall co-endemicity of onchocerciasis and lymphatic filariasis were 0.42%.

The Chi-square test indicated there is no association between onchocerciasis and lymphatic positivity with age but lymphatic filariasis has a significant association with sex (P-value= 0.014) and no significant association with age of study participants (P-Value = 0. 0559).

Co-endemicity of onchocerciasis and lymphatic filariasis in randomly selected villages

Of 372 study participants, only 4(2.7%) males were positive for lymphatic filariasis by the Oncho/LF IgG4 bi-plex test with the overall prevalence of lymphatic filariasis 1.1%. The co-endemicity of lymphatic filariasis and onchocerciasis was 1.08%.

Evaluation of the diagnostic performance of SD Bioline Oncho /LF Ig G4 bi-plex test against SD ELISA as manufacturers evaluations

The diagnostic performance of the SD Bioline oncho /LF Ig G4 bi-plex test was evaluated against SD ELISA as the gold standard test as per the manufacturer’s evaluation. From the total of 1553 purposively selected the first-line and randomly selected community samples analyzed by both Oncho/LF IgG4 bi-plex test and SD ELISA as a confirmatory test as per manufactures evaluation, 30 (1.93%) were found seropositive by both Oncho/LF IgG4 bi-plex test and SD ELISA, 8 were positive by Oncho/LF IgG4 bi-plex test but negative by SD ELISA illustrated table 7.

The overall sensitivity, specificity, positive predictive value (PPV), and negative predictive values (NPV) of the Oncho/LF Ig G4 bi-plex test in diagnosing onchocerciasis against SD ELISA as the reference standard was 26.0%, 99.93%, 96.77%, 94.42%, respectively.

In this study, a total of 1181 study participants from four first-line villages were included. The results indicated 14.43%, 11.46%, 2.91%, and 3.48% Abuko, Aroji Magala Oli, Garo, and Quban Loli first-line villages respectively. In all first-line villages, the results indicated a higher prevalence of onchocerciasis compared to the 2% WHO optimal decision to initiate MDA with ivermectin (18). The study also indicated sustained transmission of onchocerciasis in previously classified hypo-endemic areas implying the need for re-mapping and initiating MDA to ensure the progress towards elimination (12). The results envisaged the current mapping strategy of DBS test from first-line villages to initiate MDA is informative in progress towards elimination.

The prevalence of onchocerciasis among purposely included first-line villages in age categories (5–9) was 6.47%. The study result indicated serologic prevalence in children might be associated with recent infection and transmission of onchocerciasis is ongoing. The study finding is in line with WHO guidelines to stop MDA indicating serologic prevalence in children might be associated with recent infection (7, 19). The highest prevalence (12.91%) was observed in the age category of > 20 years. This is in line with the study conducted in the Semen Bench Maji Zone of Ethiopia (20). The results might be a correlated chronic infection caused by the parasite which might reside for long period in sub-cutaneous tissues without developing signs and symptoms.

Even though randomly 29 villages were not first-line villages, the prevalence of onchocerciasis among these villages was 4.6%. However, the prevalence of onchocerciasis in about 19(63%) out of 29 randomly selected villages was zero. The study indicated the need to prioritize and sub-district level mapping of hypo-endemic geographic areas taking into account the entomologic behavior of black fly vector breeding characteristics, and flight range from breeding sites for a blood meal to sustain transmission (8, 21). The study conducted in random villages’ matched-school children showed that low-intensity transmission is ongoing even in second-line villages. The study also confirmed the need to implement ivermectin MDA interventions to eliminate onchocerciasis in the district. However, mapping large-scale second-line villages and matched-school children took many days for mapping and the need to consider the availability of resources.

In this study, the co-endemicity of onchocerciasis and lymphatic filariasis was (0.42%) in fist line villages and 1.08% in random villages, and overlapping ongoing infection in matched-school children with a prevalence of onchocerciasis 0.33% and co-endemicity with lymphatic filariasis 0.25%. Study results were in line with the study conducted in Mali with a 0.18% prevalence of onchocerciasis and 0.19% lymphatic filariasis in children (22). A similar study result was also reported by Cano and his colleagues which indicated integrated disease mapping and intervention to ensure the elimination of NTDs (16). WHO calls for an integrated approach multi-sectorial approach to ensure the elimination of NTDs (21). The study conducted in Senegal indicated co-endemicity of onchocerciasis and lymphatic filariasis (23).

WHO strategic and technical advisory group for NTDs subgroup on disease-specific indicators indicated, lymphatic filariasis and onchocerciasis were co-endemic in 28 countries of the WHO in the African region, diseases targeted for elimination and share the same strategy of preventive chemotherapy to interrupt transmission using ivermectin alone or in combination with albendazole (24). Integrating and scaling up preventive chemotherapy interventions for either one or both of the diseases are essential to meet the elimination targets for each disease in these countries (24).

The sensitivity and specificity of the SD BIOLINE Oncho/LF IgG4 bi-plex test in the diagnosis of onchocerciasis is 26.09% as compared to the manufacturer’s claim of 92.42%. The manufacturer evaluated the small number of samples (211) as compared to this study which analyzed 1553 samples for evaluation. The sensitivity of Oncho/LF IgG4 bi-plex is lower than the study conducted by Steel, et al., 2015, which showed a sensitivity of 90% for Ov16 onchocerciasis (25). The study of Steel et al., 2015 analyzed a small sample size (69) as compared to the present study which analyzed a large sample size of 1553 to evaluate the diagnostic performance of the test kit.

The specificity of 99.95% of this study was in line with study reports of (25) which have shown a specificity of 98% for Ov16. The results demonstrated good specificity of the test under evaluation.

The prevalence of onchocerciasis in four first-line villages is greater than 2% of the WHO recommendation to initiate MDA with ivermectin. Both first-line and random village mapping strategies indicated greater than 2% prevalence for onchocerciasis that qualifies the district for implementation of MDA with ivermectin. While in 29 randomly selected villages, in 19(63%) of the villages, the prevalence of onchocerciasis was zero implying the need for onchocerciasis mapping at sub-district level in hypo-endemic areas. Even though the lymphatic filariasis test was conducted by tested by BIOLINE Oncho/LF Ig G4 bi-plex test only, the study indicated overlapping co-endemicity of both onchocerciasis and lymphatic filariasis and the need to integrate an elimination program in hypo-endemic areas. The sensitivity of the Oncho/LF bi-plex test is low to be used for onchocerciasis as a point-of-care test and to detect low-intensity transmission. Further large-scale evaluation is needed to use Oncho/ LF bi-plex as a point-of-care test.

The study indicated the prevalence of onchocerciasis in four first-line villages is higher than the threshold prevalence of 2% recommended by WHO to initiate MDA with ivermectin. First-line and random villages-based mapping strategies are recommended to implement MDA with ivermectin and eliminate onchocerciasis. The study indicated there was an ongoing transmission of both onchocerciasis and lymphatic filariasis in the Amaya district and overlapping co-endemicity hence integration of mapping and MDA implementation for both onchocerciasis and lymphatic filariasis is needed in the district.

Even though the study included 29 randomly selected villages, the samples were collected from house to house during the crop collection time in Ethiopia. We haven’t gotten as many samples as planned from the random communities.

African Onchocerciasis Control Program (APOC), Mass Drug Administration (MDA), Rapid Diagnostic Test(RDT), Open Data Kit (ODK), Standard Diagnostic Enzyme-linked Immunosorbent Assay (SD ELISA), Lymphatic filariasis, Neglected Tropical Diseases (NTDs), World Health Organization (WHO), Rapid Epidemiological Mapping of Onchocerciasis (REMO), Ethiopian Public Health Institute (EPHI), Statistical Package for Social Sciences (SPSS), Positive predictive values(PPV), Negative predictive values(NPV)

Acknowledgments

We would like to acknowledge laboratory professionals who have collected blood samples from the field, tested them by RDT, and made DBS for further analysis by SD ELISA, team leaders who were dedicated to organizing and continued support for the team on field and laboratory activities. We thank Regional Health Bureaus, Zonal and district health coordinators, and Amaya health center staff who were facilitating administrative issues and hosting spaces and storage of DBS until transported to the EPHI laboratory. Special thanks go to the local communities and students who were permitted to provide samples and allowed this study to happen. Likewise, we acknowledge the many school teachers and head administrators who contributed to the success of this survey. Finally, we would like to thank the Tax Force for Global Health and its staff for financial and technical support for data collection for this project.

Funding

NA

Availability of data and materials

The data sets analyzed during the current study are available from the corresponding author on reasonable request

Authors' contributions

Boja Dufera Taddese and Sindew Mekasha Feleke, conceived and designed the study and collected data, performed analysis, and interpretation of data, and also critically reviewed this manuscript. The rest author supported data collection, performed analysis, and interpretation of data, and reviewed this manuscript.

Ethical considerations

Ethical approval was obtained from the Ethics Committee of the Ethiopian Public Health Institute (EPHI) and the Ethical Review Board(EPHI-IRB). Official letters were written by the EPHI to the Regional Health and Education Bureaus to obtain regional consent. The schools directors provided written consent on behalf of the students’ families or guardians. All other teachers and students were informed about the study in their languages the purpose, the benefits, the potential risks, and the operational procedures. In addition, village leaders were informed and permission was obtained to conduct the survey. Consent was taken from each study participant before blood sample collection.

Author Contributions

Conceptualization: Boja Dufera Taddese and Sindew Mekasha Feleke.

Data curation: Sindew Mekasha and Boja Dufera Taddese.

Formal analysis: Legesse Negash and Boja Dufera Taddese.

Funding acquisition: Sindew Mekasha Feleke.

Investigators: Boja Dufera Taddese, Sindew Mekasha, Solomon Aragie, Hassen Mamo, Bacha Mekonen, Seble Seifu Semu.

Methods: Boja D. Taddese, Sindew M. Feleke.

Project administration: Boja D. Taddese and Sindew M. Feleke, Dr. Geremew Tasew Guma

Resources: Boja D. Taddese, Sindew M. Feleke.

Software: Legesse Negash.

Supervision: Sindew M. Feleke

Writing original draft: Boja D. Taddese.

Writing-review & editing: Sindew M.Feleke, Solomon Aragie and Hassen Mamo, Dr. Geremew Tasew Guma,Ahlam Awad Mohammed, Kira Barbre, Katherine Gass

Consent for publication

Participants were informed that all data collected would remain anonymous. That data would be treated statistically only and remain confidential.

Competing interests

On behalf of all authors, I state that there are no competing interests

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Table 1. Socio-demography of study participants

Study-community	Age group in years	Male (%)	Female (%)	Total (%)
First-line villages	5 - 9	142(51.1)	136(48.9)	278(100)
	10 - 20	246(48.4)	262(51.6)	508(100)
	>20	220(55.7)	175(44.3)	395(100)
Random Villages	>20	149 (40.05)	223 (50.95)	372(100)
Matched-school children	10-14	652(54.8)	551(45.8)	1203(100)
Total		1409 (51.12)	1347(48.88)	2756 (100)

Table 2. Prevalence of onchocerciasis among four first-line villages

Village’s name	SD ELISA Results		Total (%)	% Prevalence
Village’s name	Positive (%)	Negative (%)	Total (%)	% Prevalence
Abuko	44(14.4)	261(5.6)	305(100)	14.43
Quban Loli	8(2.9)	267(97.1)	275(100)	2.91
Garo	10(3.5)	277(96.5)	287(100)	3.48
Aroji Magala Oli	36(11.5)	278(88.5)	314(100)	11.46
Grand Total	98(8.3)	1083(91.7)	1181(100)	8.3

Table 3. Prevalence of onchocerciasis in first-line villages by age and sex

Age group years	Male			Female			Overall total
Age group years	Negative (%)	Positive (%)	Total	Negative (%)	Positive (%)	Total	Negative (%)	Positive (%)	Total
5-9	134(94.4)	8(5.6%)	142	126(92.4)	10(7.4)	136	260(93.5)	18(6.5)	278
10-20	229(93.1)	17(6.9)	246	250(95.4)	12(4.6)	62	479(94.3)	29(5.7)	508
>20	181(82.3)	39(17.7)	220	163(93.1)	12(6.9)	75	344(87.1)	51(12.9)	395
Total	544(89.47)	64(10.53)	608	539(94.1)	34(5.9)	573	1083(92.7)	98(8.3)	1181

Table 4. Prevalence of onchocerciasis in randomly selected villages

Sr No	Name of villages	SD ELISA Results
Sr No	Name of villages	Positive (%)	Negative (%)	Total (%)	% Prevalence
1	Sudo	3(21.4)	11(78.6)	14	21.4
2	Tiro Ilala	3(20)	12 (80)	15	20
3	Hudad-7	1(7.1)	13(92.9)	14	7.1
4	Abuye Jabilala	1(14.3)	6 (85.7)	7	14.3
5	Gombore Aliye	1(7.7)	12 (92.3)	13	0
6	Gombore	2(13.3)	13 (86.7)	15	0
7	Balchi-10	2(9.1)	20 (90.9)	22	4.5
8	Balchi 12	0	6 (100)	6	0
9	Agamiti oli	1(14.3)	6 (85.7)	7	14.3
10	Lafto gidu	1(4.5)	21(95.5)	22	0
11	Xatesa first	0	12 (100)	12	0
12	Mito baha	0	14 (100)	14	0
13	Kile	1(16.7)	5 (83.3)	6	0
14	Edo Lenca	0	8 (100)	8	0
15	Gibe	0	10 (100)	10	0
16	Kilmi	0	9 (100)	9	0
17	Dire	0	13 (100)	13	0
18	Bareda gidu	0	14 (100)	14	0
19	Oshore	0	6 (100)	6	0
20	Abado	0	15 (100)	15	0
21	Kiro gadi	0	19 (100)	19	0
22	Mamudi	0	19 (100)	19	0
23	xumi	0	10 (100)	10	0
24	Abado hole 5	0	13 (100)	13	0
25	Sefere Ajo	0	14 (100)	14	0
26	Gindo 02	1(8.3)	11 (91.7)	12	0
27	Mari gadi	0	23 (100)	23	0
28	Desta	0	14 (100)	14	0
29	Teltele Baha	0	6 (100)	6	0
	Total	17(4.57)	355 (95.43)	372 (100)	17 (4.56)

Table 5. Prevalence of onchocerciasis among matched school children in randomly selected villages

Sr. N	School’s name	Onchocerciasis
Sr. N	School’s name	Positive N, (%)	Negative N, (%)	Total N
1	Ilala	1 (1.59)	62 (98.41)	63
2	Hudad-2	2 (3.13)	52 (96.88)	54
3	Abuye Jabila	1 (1.47)	67 (98.53)	68
4	Gombore	0 (0)	55 (100)	55
5	Darge Qota	0 (0)	55 (100)	55
6	Gamte	0 (0)	49 (100)	49
7	Lafto tsige	0 (0)	51 (100)	51
8	Kono kolti	0 (0)	50 (100)	50
9	Denkaka	0 (0)	43 (100)	43
10	Yaya	0 (0)	54 (100)	54
11	Kura Bula	0 (0)	54 (100)	54
12	Kacam	0 (0)	41 (100)	41
13	Qara kile	0 (0)	21 (100)	21
14	Bareda	0 (0)	47 (100)	47
15	Muri	0 (0)	66 (100)	66
16	Arbeseden	0 (0)	52 (100)	52
7	Mamudi	0 (0)	50 (100)	50
18	Bino	0 (0)	50 (100)	50
19	Abado Hole	0 (0)	41 (100)	41
20	Gilmer of Hope	0 (0)	63 (100)	63
21	Amaya	0 (0)	42 (100)	42
22	Meri	0 (0)	40 (100)	40
23	Sekela	0 (0)	46 (100)	46
24	Bulti Samon	0 (0)	48 (100)	48
Total		4 (3.33)	1,199 (96.67)	1203 (100)

Table 6.Prevalence of lymphatic filariasis in four first-line villages

Villages name	Biplex results of lymphatic filariasis			% prevalence of lymphatic filariasis
Villages name	Positive (%)	Negative (%)	Total (%)	% prevalence of lymphatic filariasis
Abuko	11(3.6)	294 (96.4)	305 (100)	3.6
Quban loli	0 (0)	275 (100)	275 (100)	0
Garo	0 (0)	287 (100)	287 (100)	0
Aroji magala oli	1(0.3)	313 (99.7)	314 (100)	0.3
Total	12(1.02)	1169 (98.08)	1181(100)	1.02

Table 7: Two by two tables Oncho/LF IgG4 bi-plex against SD ELISA

Biplex test	SD ELISA Results		Total
Biplex test	Positive (%)	Negative (%)
Positive	30	1	31
Negative	85	1437	1522
Total	115	1438	1553

No competing interests reported.

Evaluation of epidemiological mapping strategies and diagnostic tool for onchocerciasis and lymphatic filariasis in hypo-endemic Amaya district, South-Western Ethiopia

Status:

Version 1

Abstract

Background

Methods

Study design, area, population, and sampling techniques

Blood sample collection and laboratory testing

Data management and analysis

Results

Socio-demography of study participants, randomly selected and matched school children

Prevalence of onchocerciasis among four first-line villages

Prevalence of onchocerciasis by age and sex from four first-line villages

Prevalence of onchocerciasis among randomly selected villages

Prevalence of onchocerciasis among matched school children in randomly selected villages

Prevalence of lymphatic filariasis among first-line villages

Prevalence of lymphatic filariasis among randomly selected villages

Prevalence of lymphatic filariasis in matched-school children in randomly selected villages

Co-endemicity of onchocerciasis and lymphatic filariasis in first-line villages

Co-endemicity of onchocerciasis and lymphatic filariasis in randomly selected villages

Evaluation of the diagnostic performance of SD Bioline Oncho /LF Ig G4 bi-plex test against SD ELISA as manufacturers evaluations

Discussion

Conclusions

Recommendation

Limitations of the study

Abbreviations

Declarations

References

Tables

Additional Declarations

Status:

Version 1