Integrated Serosurveillance for Onchocerciasis, Lymphatic Filariasis, and Schistosomiasis in North Darfur, Sudan.

Sudan is endemic for multiple neglected tropical diseases, including trachoma, onchocerciasis (OV), lymphatic filariasis (LF), and schistosomiasis (SCH). In 2019, dried blood spot samples were collected for a baseline trachoma serosurvey in three localities (El Seraif, Kotom, and Saraf Omrah) in North Darfur State. None were classified previously as OV- or LF-endemic, although low levels of SCH had been identified in all three. Approximately 30 households from 25 communities in each locality were selected by multistage cluster random sampling. Collections of DBSs were analyzed by multiplex bead assay for antibodies to multiple pathogens. This paper presents data on OV (Ov16), LF (Wb123, Bm14, Bm33), and SCH (soluble egg antigen [SEA], Sm25) antibodies among 8,322 individuals from 2,119 households. The survey-adjusted seroprevalence estimates for Ov16 were <0.3% in all localities. Lymphatic filariasis-antigen seroprevalences were discordant. Seroprevalence estimates ranged from 4.6-6.0% (Wb123), 0.99-1.4% (Bm14), and 29.2-33.3% (Bm33). Schistosomiasis seroprevalence estimates among school-aged children ranged from 2.7-8.0% (SEA) and 10.9-15.6% (Sm25). Ov16 seropositivity was low and supported the localities' classification as nonendemic. The results suggested LF exposure, but discordance between antigens, challenges defining seropositivity thresholds, and the absence of programmatic guidance based on antibody serology alone for Wuchereria bancrofti indicate a need for remapping surveys to confirm transmission. Schistosomiasis antibody levels were high enough to warrant further mapping to guide treatment decisions. The lack of gold standards limited interpretation of results, particularly for LF, but in resource-challenged areas, integrated serological surveillance offers the possibility of efficient monitoring of exposure to multiple diseases.

Socioeconomic impacts of elimination of onchocerciasis in Abu-Hamed focus, northern Sudan: lessons after elimination.

OBJECTIVES: Onchocerciasis is one of the most devastating neglected tropical diseases and it is mostly prevalent in Africa. The disease has important heavy social and economic burdens on the infected populations including low productivity, unemployment, social isolation, and stigma. A cross-sectional study was implemented using a well-established questionnaire to investigate the socio-economic impacts of Onchocerciasis elimination in Abu-Hamed, River Nile State, Sudan in 2015; 512 participants in ten affected communities were interviewed. RESULTS: Our findings revealed that these communities are recovering from the social and economic burden of the diseases. Ninety percent of the research participants reported general satisfaction about elimination of the disease in their community, 48.3% of them attended secondary school or university. Only 0.6% reported unemployment. Also, 25.3% and 24.7% of the participants were workers and farmers respectively. Except about the vector biting and nuisance, the majority of the respondents (90%) had no complain related to the disease after the elimination. Also, 90.5% of the participants reported either stable or increase in their work performance during the last 12 months. About 93.8% of the respondents were engaged in normal daily life activities and involved in happy events like marriage and giving birth during the last 12 months.

The Galabat-Metema cross-border onchocerciasis focus: The first coordinated interruption of onchocerciasis transmission in Africa.

BACKGROUND: Onchocerciasis transmission across international borders is not uncommon, yet a coordinated cross border stops mass drug administration (MDA) decision has not been documented. METHODS/PRINCIPLE FINDINGS: The Galabat-Metema focus involves neighboring districts on the border between Sudan and Ethiopia. Mass drug administration (MDA) was provided once and subsequently twice per year in this focus, with twice-per-year beginning in Ethiopia's Metema subfocus in 2016 and in the Sudan's Galabat subfocus in 2008. Ov16 ELISA-based serosurveys were conducted in 6072 children under 10 years of age in the Metema subfocus in 2014, and 3931 in the Galabat in 2015. Between 2014 and 2016, a total of 27,583 vector Simulium damnosum flies from Metema and 9,148 flies from Galabat were tested by pool screen PCR for Onchocerca volvulus O-150 DNA. Only 8 children were Ov16 seropositive (all in the Metema subfocus); all were negative by skin snip PCR. The upper limit of the 95% confidence interval (UCL) for Ov16 seropositive was <0.1% for the overall focus and 0.14 positive fly heads per 2000 (UCL = 0.39/2000). However, an entomological 'hotspot' was detected on the Wudi Gemzu river in Metema district. The hotspot was confirmed when 4 more positive fly pools were found on repeat testing in 2017 (1.04 L3/2000 flies (UCL = 2.26/2000). Information exchange between the two countries led to stopping MDA in a coordinated fashion in 2018, with the exception of the hotspot at Wudi Gemzu, where MDA with ivermectin was increased to every three months to hasten interruption of transmission. CONCLUSION: Coordinated stop MDA decisions were made by Sudan and Ethiopia based on data satisfying the World Health Organization's criteria for interruption of onchocerciasis transmission. Definitions of entomological 'hotspots' and buffer zones around the focus are proposed.

The positive influence the Onchocerciasis Elimination Program for the Americas has had on Africa programs.

A recent article "Is onchocerciasis elimination in Africa feasible by 2025: a perspective based on lessons learnt from the African control programmes" in Infectious Diseases of Poverty claimed that undue influence on African programs by concepts developed by the Onchocerciasis Elimination Program of the Americas (OEPA) is detrimental to stopping mass drug administration (MDA) in Africa. This claim is made despite a record year for MDA stoppage in four African countries of > 3.5 million treatments in 2018, far exceeding any past OEPA or African Program for Onchocerciasis Control (APOC) stop MDA success.

Notes on distribution of Simulium damnosum s. l. along Atbara River in Galabat sub-focus, eastern Sudan.

BACKGROUND: Onchocerciasis is caused by a nematode worm Onchocerca volvulus, which is transmitted in Sudan by black fly vectors of the Simulium damnosum sensu lato species complex. In Sudan, the disease is found in four foci where fast flowing rivers provide suitable breeding sites for the Simulium vector flies. The construction of dams and irrigation schemes for agricultural purposes has affected black fly breeding and distribution, such as in Merowe Dam in Abu-Hamed focus, where the perennially flowing water downstream of the Dam created new vector breeding sites, thereby, changing the pattern of disease transmission and creating public health problems. Based on this situation, this study was carried out to measure the effect of the Upper Atbara and Setit Dam complex on the distribution of Simulium damnosum s.l. breeding sites and on disease elimination in the Galabat sub-focus in eastern Sudan. METHODS: Aquatic stages of Simulium were collected between October and November 2009, prior to the construction of the dam complex, and again in 2013 and 2015 while the dam complex construction was ongoing. RESULTS: A total of 40 breeding sites were identified at the beginning of the study. After the construction of the dam complex in 2015, seventeen previously mapped breeding sites were inaccessible as they had been flooded by the dam complex's lake when reach its maximum size. Three species were obtained from different locations: S. damnosum s.l., S. griseicolle, and S. adersi. CONCLUSIONS: This study has shown a link between the construction of the dam complex and a reduction in the breeding sites of black fly vectors. This reduction has limited the Galabat sub-focus to a small area at the upper Atbara River which become the end of the focus. To sustain the success achieved in onchocerciasis control in the Galabat sub-focus, disease control and its vector control should be strengthened in the area cross-boarding Sudan and Ethiopia.

Evidence of pre-existing active Zika virus circulation in Sudan prior to 2012.

OBJECTIVE: The purpose of this study is to provide the first evidence of Zika virus circulation (ZIK) in Sudan. Zika virus was first isolated in the Zika forest of Uganda in 1947, and in 2016, the World Health Assembly declared it a public health emergency of international concern. The discovery of Zika virus circulation in Sudan came as a secondary finding in a 2012 country-wide yellow fever prevalence study, when laboratory tests were done to exclude cross-reactions between flaviviruses. The study was cross-sectional community-based, with randomly selected participants through multi-stage cluster sampling. A sub-set of samples were tested for the Zika virus using ELISA, and the ones that demonstrated reactive results were subsequently tested by PRNT. RESULTS: The prevalence of Zika IgG antibodies among ELISA-tested samples was 62.7% (59.4 to 66.1, 95% CI), and only one sample was found positive when tested by PRNT. This provided the first documented evidence for the pre-existing circulation of Zika virus circulation in Sudan. This evidence provides the foundation for future research in this field, and further structured studies should be conducted to determine the epidemiology and burden of the disease.

The First Confirmed Elimination of an Onchocerciasis Focus in Africa: Abu Hamed, Sudan.

Mass treatment with ivermectin for onchocerciasis was stopped in 2012 in Abu Hamed, an isolated focus on the River Nile in northern Sudan. A 3-year posttreatment surveillance (PTS) ensued, at the end of which an evaluation was conducted in 2015 following the current World Health Organization guidelines for verification of onchocerciasis elimination. Vector black flies were collected from sentinel breeding sites and finger-prick bloodspots were collected from children ≤ 10 years of age resident in 35 communities within the focus. Polymerase chain reaction (PCR) screening of 19,191 flies from four sites for the O-150 parasite-specific marker found no flies carrying Onchocerca volvulus larvae (0%, 95% upper confidence limit [UCL] = 0.16), and serological testing of 5,266 children identified only one Ov16 seropositive child (0.019%, 95% UCL = 0.074); whose skin snips were negative when tested by O-150 PCR assay. These results indicate that for the first time in Africa, onchocerciasis elimination has been verified after a successful PTS in Abu Hamed.

Seasonal Variation in Biting Rates of Simulium damnosum sensu lato, Vector of Onchocerca volvulus, in Two Sudanese Foci.

BACKGROUND: The abundance of onchocerciasis vectors affects the epidemiology of disease in Sudan, therefore, studies of vector dynamics are crucial for onchocerciasis control/elimination programs. This study aims to compare the relative abundance, monthly biting-rates (MBR) and hourly-based distribution of onchocerciasis vectors in Abu-Hamed and Galabat foci. These seasonally-based factors can be used to structure vector control efforts to reduce fly-biting rates as a component of onchocerciasis elimination programs. METHODS: A cross-sectional study was conducted in four endemic villages in Abu-Hamed and Galabat foci during two non-consecutive years (2007-2008 and 2009-2010). Both adults and aquatic stages of the potential onchocerciasis vector Simulium damnosum sensu lato were collected following standard procedures during wet and dry seasons. Adult flies were collected using human landing capture for 5 days/month. The data was recorded on handheld data collection sheets to calculate the relative abundance, MBR, and hourly-based distribution associated with climatic factors. The data analysis was carried out using ANOVA and Spearman rank correlation tests. RESULTS: Data on vector surveillance revealed higher relative abundance of S. damnosum s.l. in Abu- Hamed (39,934 flies) than Galabat (8,202 flies). In Abu-Hamed, vector populations increased in January-April then declined in June-July until they disappeared in August-October. Highest black fly density and MBR were found in March 2007 (N = 9,444, MBR = 58,552.8 bites/person/month), and March 2010 (N = 2,603, MBR = 16,138.6 bites/person/month) while none of flies were collected in August-October (MBR = 0 bites/person/month). In Galabat, vectors increased in September-December, then decreased in February-June. The highest vector density and MBR were recorded in September 2007 (N = 1,138, MBR = 6,828 bites/person/month) and September 2010 (N = 1,163, MBR = 6,978 bites/person/month), whereas, none appeared in collection from April to June. There was a significant difference in mean monthly density of S. damnosum s.l. across the two foci in 2007-2008 (df = 3, F = 3.91, P = 0.011). Minimum temperature showed significant correlation with adult flies counts in four areas sampled; the adult counts were increased in Nady village (rs = 0.799) and were decreased in Kalasecal (rs = -0.676), Gumaiza (rs = -0.585), and Hilat Khateir (rs = -0.496). Maximum temperature showed positive correlation with black fly counts only in Galabat focus. Precipitation was significantly correlated with adult flies counts in Nady village, Abu-Hamed, but no significance was found in the rest of the sampled villages in both foci. Hourly-based distribution of black flies showed a unimodal pattern in Abu-Hamed with one peak (10:00-18:00), while a bimodal pattern with two peaks (07:00-10:00) and (14:00-18:00) was exhibited in Galabat. CONCLUSION: Transmission of onchocerciasis in both foci showed marked differences in seasonality, which may be attributed to ecology, microclimate and proximity of breeding sites to collection sites. The seasonal shifts between the two foci might be related to variations in climate zones. This information on black fly vector seasonality, ecology, distribution and biting activity has obvious implications in monitoring transmission levels to guide the national and regional onchocerciasis elimination programs in Sudan.

The impact of Merowe Dam on Simulium hamedense vector of onchocerciasis in Abu Hamed focus - Northern Sudan.

BACKGROUND: Abu Hamed, the northernmost onchocerciasis focus in the world, is located along the River Nile banks in the Nubian Desert. Hydroelectric dams can alter activity of black flies and may provide breeding sites for black fly. Merowe Dam, the largest hydropower project in Africa, was built west of Abu Hamed focus in 2009. The impact of the Dam on onchocerciasis and its black fly vectors in Abu Hamed focus was measured in this study. FINDINGS: Entomological surveys for aquatic stages and adult Simulium hamedense were conducted before and after the inception of Merowe Dam in 2007/2008 and 2010/2011. There was no black fly breeding or adult activity in the previously known breeding sites upstream of the Merowe Dam with the western most breeding site found in AlSarsaf village near the center of the focus. No adult or aquatic stages of black flies were found downstream of the Dam. CONCLUSIONS: The artificial lake of the Dam flooded all the breeding sites in the western region of the focus and no aquatic stages and/or adult black fly activity were established in the study area upstream of the Dam. The Dam seems to have positive impact on onchocerciasis and its black fly vectors in Abu Hamed focus. These outcomes of the Merowe Dam might have contributed to the recently declared interruption of onchocerciasis transmission in Abu Hamed focus. Continuous entomological surveys are needed to monitor presence of black fly vectors and its impact on the disease.

Interruption of Onchocerca volvulus transmission in the Abu Hamed focus, Sudan.

Abu Hamed, Sudan, the northernmost location of onchocerciasis in the world, began community-directed treatment with ivermectin (CDTI) in 1998, with annual treatments enhanced to semiannual in 2007. We assessed the status of the parasite transmission in 2011 entomologically, parasitologically, and serologically. O-150 pool screening showed no parasite DNA in 17,537 black flies collected in 2011 (95% confidence interval upper limit [95% CI UL] = 0.023). Skin microfilariae, nodules, and signs of skin disease were absent in 536 individuals in seven local communities. Similarly, no evidence of Onchocerca volvulus Ov16 antibodies was found in 6,756 school children ≤ 10 years (95% CI UL = 0.03%). Because this assessment of the focus meets the 2001 World Health Organization (WHO) criteria for interrupted transmission, treatment was halted in 2012, and a post-treatment surveillance period was initiated in anticipation of declaration of disease elimination in this area. We provide the first evidence in East Africa that long-term CDTI alone can interrupt transmission of onchocerciasis.

Polymerase chain reaction pool screening used to compare prevalence of infective black flies in two onchocerciasis foci in northern Sudan.

Onchocerciasis remains an important debilitating disease in many areas of Africa, including Sudan. The status of infection transmission in 2007 was assessed in the vectors of two disease foci in Sudan: Abu Hamed in northern Sudan, which has received at least 10 years of annual treatment and Galabat focus in eastern Sudan, where only minor, largely undocumented treatment activity has occurred. Assessment of more than 30,000 black flies for Onchocerca volvulus infectious stage L3 larvae by using an O-150 polymerase chain reaction protocol showed that black fly infectivity rates were 0.84 (95% confidence interval = 0.0497-1.88) per 10,000 flies for Abu Hamed and 6.9 (95% confidence interval = 1.1-16.4) infective flies per 10,000 for Galabat. These results provide entomologic evidence for suppressed Onchocerca volvulus transmission in the Abu Hamed focus and a moderate transmission rate of the parasite in the Galabat focus.