Table 3.
Details of the studies in which monitoring was done during MDA
| Study no. | Region | Country | Author & year | No. of districts or villages or sites | No. of people tested | Age (years) | Indicator | Findings |
|---|---|---|---|---|---|---|---|---|
| 1 | Americas | Haiti | Hochberg et al, 2006103 | Five sites | 3,781 persons | All ages | Ag prevalence | In this study, the researchers had explored the occurrence of systemic symptoms (fever, dizziness, headache, pruritus and myalgias) after the 5th round of MDA and its relation to filarial infection (Ag using ICT). Those who returned to the distribution posts seeking treatment of symptoms after the MDA were interviewed. Results showed that majority of the people reporting systemic and scrotal symptoms did not have detectable Ag levels at the time of reporting. The authors concluded that given the low doses of DEC and albendazole used in the MDA, it is less likely that the reported symptoms were caused by drug-related side effects. However, they queried whether treating such symptoms as a part of surveillance would affect MDA coverage and that it would vary from country to country. |
| 2 | South East Asia | India | Mukhopadhyay et al, 2007104 | Two urban areas and six rural villages of East godavari district | 5,056 persons | All ages | Mf, disease and vector infection prevalence | East Godavari district in Andhra Pradesh, India had undergone six rounds of MDA from 1999 to 2005. Mf and entomological surveys were conducted in six villages and 2 towns of the district. The Mf and disease rates were 4.4% and 2.4% respectively. The vector infection and infectivity rates were 3.6 and 0,4% respectively. It stressed on the need to develop strategies to implement MDA more effectively by increasing the drug compliance. |
| 3 | South East Asian | India | Yuvaraj et al, 2008105 | 15 villages, Villupuram district | Not mentioned | >15 | Hydrocele prevalence | This study was conducted during a long term community based trial to measure the effectiveness of MDA with DEC alone or Ivermectin alone where the coverage under MDA ranged between 54–75%. Cross-sectional clinical surveys were carried out before and after seven rounds of MDA. After seven rounds, hydrocele prevalence had declined from the pre-intervention level of 20.5–5.1% (P<0.05) in the DEC arm, from 23.9% to 10.4% (P<0.05) in the ivermectin arm and from 20.4% to 10.9% (P<0.05) in the placebo arm, equivalent to reductions of 75.3%, 56.6% and 46.6%, respectively. However there was only a marginal decrease in lymphoedema in both arms. After the seventh MDA, there was a statistically significant decline in hydrocele prevalence in all other age groups in the communities treated with DEC. The impact was relatively less in ivermectin arm. Repeated DEC administration has the potential to prevent incidence of new hydrocele cases and may resolve the manifestation at least in a proportion of affected people. |
| 4 | Western Pacific | Samoa | Joseph et al 2011106 | Five villages | 2,474 persons | All ages & ≤10 | Mf, Ag and Ab prevalence | In Samoa, inspite of 6 rounds of MDA, post treatment survey showed persistent Ag in one of the islands. Mf, Ag and Ab surveys (CELISA kit) were carried out to assess if transmission had interrupted in this island with persistent infection and in another island where transmission had interrupted. Results showed the need for strengthened control effects in these areas. The area, which was declared LF free was found to be endemic based on Ab survey in children. It concluded that more studies were required to validate the use of CELISA as a tool for assessing transmission. |
| 5 | Western Pacific | Papua New Guinea | Tisch et al, 2011107 | Dreikikir district of East Sepik Province | Not mentioned | ≥5 years | Disease prevalence | This study measured the impact of an MDA trial (with single dose of DEC alone vs single dose of DEC plus ivermectin) after 4 rounds on acute filariasis morbidity(AFM) using a questionnaire. The annual incidence of AFM decreased by 20% during the year following the first MDA and by 49–61% in subsequent years relative to pre-MDA rates. AFM rates did not differ according to microfilaremic status or density (categorized as 0, 1–9, 10–99 and 100 microfilaria per ml) during any other study periods. Risk factor analysis showed that age, residence, Mf positivity, not taking MDA drugs were at greater risk of developing AFM. The authors concluded that the incidence of AFM in this population decreased to 57% of the pre-treatment level after 2 annual MDAs in areas of moderate transmission and by 61% in areas of high transmission irrespective of the drugs used for MDA. This rapid decrease in AFM incidence was sustained over the entire 5-year surveillance period, thereby highlighting the potential of MDA to alleviate this feature of LF morbidity. |
| 6 | South East Asia | India | Shriram et al, 2014108 | Five islands of Andaman and Nicobar islands | 2,561 persons | All ages | Mf prevalence | Transmission Assessment surveys (TAS) to decide on stopping or continuing MDA was carried out in a lone foci of infection, Nancowry group of Islands. It was found that inspite of 6 rounds of MDA, Mf prevalence was 3.3%. The authors had suggested mass distribution of DEC medicated salt as an adjunct to hasten elimination of infection in these islands. |
| 7 | South East Asia | Indonesia | Dewi et al, 2015109 | Three communities (one non endemic, one passed TAS, one failed TAS) |
1,543 children | 6–7 | Ab prevalence | This study provided the epidemiological support for the use of Ab levels to determine “critical cut-off thresholds” in Brugia spp. areas. Results from districts which followed the current WHO guidance for mapping, MDA, and implementing TAS, while providing Ab profiles of treated and untreated populations under programmatic settings, supported the choice of Ab prevalence in the 6 and 7yo group in TAS for stopping MDA decisions. |
| 8 | Africa | Ethiopia | Endeshaw et al, 2015110 | Three villages | 774 persons | ≥2 | Ag prevalence | It assessed the impact of 7 years of annual MDA with IVM monotherapy for oncho on LF and showed that it did not interrupt LF transmission. If LF was to be targeted along with oncho in the control program, albendazole should be added and treatment coverage should be improved. |
| 9 | South East Asia | Bangladesh | Hafiz et al, 2015111 | 30 villages of Nilphamari district | 1,242 persons | All ages | Acute disease prevalence | The study assessed the impact of 12 rounds of MDA on clinical filariasis. A two-stage 30 cluster survey with selected villages were surveyed for Ag (ICT), episodes of ADLA and chronic LF manifestations. The study villages and the disease cases were mapped. Results showed there was no association between disease status and filarial Ag positivity. Twenty one of the 30 villages recorded at least one manifestation. Disease prevalence was 4.4 (3.4–5.7). The authors suggested the use of mobile apps for geo referencing the disease database at village level which may be helpful for scaling up MMDP activities and a home-based morbidity control protocol. However, there was no baseline information on disease in these areas to relate the change to the impact of MDA. |
| 10 | Africa | Senegal | Wilson et al, 2016112 | 14 villages in three districts | 1,131 persons | ≥5 | Ag and Ab prevalence | It assessed the possibility of adding LF tests to a standard onchocerciasis epidemiological survey to provide meaningful results for LF-onco elimination program. The status of LF in three districts was assessed using ICT and Wb123, along with the Ov16 RDT in Kedougou region of Senegal, co-endemic for both oncho and LF. A convenience sample of individuals from 14 villages from three districts were examined for both W. bancroftiand O. volvulusinfection. Prevalence of LF antigen was found as 0.5% (95%CI: 0.2–1.2%) and that of its antibody was 0.6% (0.2–1.3%). However, one of the three districts, Salemata recorded an Ag and Ab prevalence of 3.5% (1.3–7.4%) and 1.2% (0.2–4.2%). TAS required a sample of 1,500 children to assess interruption of LF transmission but in the current study the sample size was small and therefore it could not be determined if transmission was interrupted even if no ICT positives were detected. The findings of this study provided insight into the complexities that may arise if the stop MDA decision was to be taken in LF and Oncho co-endemic areas. |
| 11 | Africa | Ethiopia | Mengistu et al, 2017113 | 70 districts | Not mentioned | Not mentioned | Mf and Ag prevalence | The study described the current status of the LF elimination programme that was integrated with the onchocerciasis control program in 2009 that was implemented in 70 LF endemic districts. By 2016 it had achieved 100% geographical coverage with treatment coverages between 73 and 87% and an epidemiological coverage of 65%. Being a malarious region too, LLIN distribution and IRS also played a significant role in prevention of LF. The current status indicated that Ethiopia was poised to achieve the 2020 goal of elimination of LF if the treatment coverage was sustained and strong monitoring and evaluation were in place. |
| 12 | South East Asia | India | Vaishnav et al, 2007114 | One city (Surat) | 5,058 persons | ≥1 | Mf prevalence | This study assessed the LF situation after 6 rounds of MDA in Surat ciy. LF endemicity rate reduced from 0.24% to 0.11% (reduction 54%) and in north zone it reduced from 0.72% to 0.30% (reduction of 58%). Though, overall Mf rate had reduced due to MDA, higher rate was noticed in North zone of city where the migrant populations influx was higher. |
| 13 | South East Asia | India | Khan et al, 2015115 | Tea garden population of Dibrugarh, Assam | 634 persons | All ages | Mf, disease and vector infection prevalence | The study assessed the current filariasis situation after five rounds of MDA among tea garden workers in Assam who had recorded high Mf rates in the past. Mf, disease and entomological surveys were conducted. While Mf rate was 3.8%, disease rate was 5.7%. Vector infection (13.2%) and infectivity (3.7%) rates were high. While the distribution coverage was >80% in 2007, it reduced to 60–70% in 2013. However, there were no information on the compliance rates. The study concludes that LF elimination in the State is achievable but poor drug compliance was the main bottleneck to the elimination program. Community participation in adjunct to training of drug distributors for meeting the target of drug compliance were the essential components in the success of GPELF. |
| 14 | Africa | Tanzania | Simonsen et al, 2010116,117 | One village (Kirare) | 919 persons | ≥1 | Mf, Ag and Ab prevalence | These two studies from Tanzania, utilized the data from the surveys conducted in the Kirare village in Africa, which had completed four rounds of MDA. All individuals (only residents) in the village were examined under Mf, Ag(Og4C3) and Ab(Bm14) at the baseline and after each round of MDA upto 3rd MDA. Entomological surveys were also carried out for monitoring infection in vectors. However, children enrolled and assessed for Ag in standard Iimmediately after first MDA were followed upto 4th MDA and antigen levels were measured in them prior to each MDA. Results of these studies indicate that the prevalence of Ag and Ab post-4 MDA did not differ significantly from baseline levels. However, there were significant difference in Ag units and Ab OD values among the cohorts of individuals surveyed at both time points (Og4C3 Ag units: from 106.9 to 47.3 CFA units and Ab OD value: (from to 0.784 to 0.405). With regard to vector infection, the reduction was significant even after the first round of MDA. However the reduction in vector infectivity rates was not significant. Even the mean monthly transmission potential decreased by 87 times post 4th MDA. Ag prevalence in children of standard I immediately before the first MDA reduced significantly after 2 MDA onwards and reached 6.4% from 25.5%after the 4th MDA. |
| 15 | Africa | Tanzania | Simonsen et al, 2011 | 10 rural primary schools | 700–800 children | 6–14 | Ag prevalence | |
| 16 | Americas | Haiti | Boyd et al, 2010118 | Six villages | 455 persons | 2-4 | Mf, Ag and Ab prevalence | The authors described how even if the sentinel sites reported Mf prevalences <1%, after eight rounds of MDA, transmission could still continue to occur through a 30-cluster survey among 2-4 yo. Ag and Ab prevalences were 14.3% and 19.7%. Filarial infection was focal in nature and infection was significantly associated with non-compliance to MDA drugs. |
| 17 | Africa | Nigeria | Richards et al, 2011119 | 10 villages | 10,753 persons | ≥2 | Mf, Ag and vector infection prevalence | The study assessed the impact of MDA (7 years of monotherapy with IVM in 12 LGAs) in a LF-Oncho co-endemic area. The villages were annually monitored till 2009, for both human and vector infection since 2000 and had completed 7–10 rounds of MDA with a coverage of 72% in 2003, ≥85% in 2006 and 73% by 2009. Impact on transmission showed that by 2009 Mf prevalence decreased from 4.9% to 0.8% (86% reduction), Ag (based on ICT) from 21.6% to 7.2% (67% reduction), vector infection from 3.1 to 0.4 (86% reduction) and infectivity rate from 1.3 to 0.3% (77% reduction). Three sentinel villages had on-going transmission (based on infective L3 in mosquito) and one had a Ag prevalence of 27.3% and vector infection >2%, indicating the need for increased interventional efforts. The authors suggested that LGAs with greater endemicity (≥25% Ag prevalence at baseline) were likely to be the primary areas of risk of MDA failure. As the remaining LGAs were on the path of making decisions on stopping MDA, particularly for a co-endemic area there were two options: (i) IVM alone may have to be continued with post MDA surveillance for LF to prevent its recrudescence or (ii) after assessing the status of oncho transmission, if found interrupted stop Oncho MDA, and plan for an integrated surveillance method to carry out post-MDA surveillance for both the diseases. |
| 18 | Western Pacific | American Samoa | Mladonicky et al, 2009120 | Three villages | 579 persons | ≥5 | Ag and Vector infection prevalence | The use of Ab and xeno monitoring in LF transmission was explored in an area that had completed 6 rounds of MDA. Mf, Ag and Ab surveys were conducted in three villages covering individuals aged >4 years. The overall prevalence of Mf was <1%, Ag prevalence ranged between 3.7 and 4.6% and Ab prevalence ranged between 12.5% and 14.9% in all these villages. As there were reports of vector infection in these villages (based on an earlier study), the authors concluded that both xeno-monitoring and Ab may be useful to identify areas with potential transmission of LF. |
| 19 | Eastern Mediterranean | Egypt | Farid et al, 2007121 | Two sentinel sites | Not mentioned | All ages | Mf, Ag and Vector infection prevalence | The study was conducted in Egypt, after five rounds of MDA to appraise if MX can be used as a tool for assessing progress towards elimination of LF. The tool was tested in two sentinel villages to measure the parasite DNA rates in mosquitoes. Results showed that the parasite DNA rates reduced by 93.8% and 100% in high and low prevalence areas respectively after five rounds of MDA. These changes were consistent with decreases in Mf prevalence rates in the sites. It also provided insight regarding the minimal mosquito DNA rates necessary for sustained transmission of filariasis in Egypt. The study concluded that MX is a powerful tool for assessing the impact of MDA. |
Abbreviations: LF, Lymphatic filariasis; DEC, Diethylcarbamazine; IVM, Ivermectin; Ag, Antigeneamia; Mf, Microfilaraemia; Ab, Antibody; MDA, Mass drug administration; TAS, Transmission Assessment Survey; ICT, Immunochromatographic Test; MX, Molecular Xenomontoring.