Controlling lymphatic filariasis and soil-transmitted helminthiasis together in South Asia: opportunities and challenges

Soil-transmitted helminths: A critical review of the impact of co-infections and implications for control and elimination

Researchers have raised the possibility that soil-transmitted helminth (STH) infections might modify the host's immune response against other systemic infections. STH infections can alter the immune response towards type 2 immunity that could then affect the likelihood and severity of other illnesses. However, the importance of co-infections is not completely understood, and the impact and direction of their effects vary considerably by infection. This review synthesizes evidence regarding the relevance of STH co-infections, the potential mechanisms that explain their effects, and how they might affect control and elimination efforts. According to the literature reviewed, there are both positive and negative effects associated with STH infections on other diseases such as malaria, human immunodeficiency virus (HIV), tuberculosis, gestational anemia, pediatric anemia, neglected tropical diseases (NTDs) like lymphatic filariasis, onchocerciasis, schistosomiasis, and trachoma, as well as Coronavirus Disease 2019 (COVID-19) and human papillomavirus (HPV). Studies typically describe how STHs can affect the immune system and promote increased susceptibility, survival, and persistence of the infection in the host by causing a TH2-dominated immune response. The co-infection of STH with other diseases has important implications for the development of treatment and control strategies. Eliminating parasites from a human host can be more challenging because the TH2-dominated immune response induced by STH infection can suppress the TH1 immune response required to control other infections, resulting in an increased pathogen load and more severe disease. Preventive chemotherapy and treatment are currently the most common approaches used for the control of STH infections, but these approaches alone may not be adequate to achieve elimination goals. Based on the conclusions drawn from this review, integrated approaches that combine drug administration with water, sanitation and hygiene (WASH) interventions, hygiene education, community engagement, and vaccines are most likely to succeed in interrupting the transmission of STH co-infections. Gaining a better understanding of the behavior and relevance of STH co-infections in the context of elimination efforts is an important intermediate step toward reducing the associated burden of disease.

Monitoring the Status of Soil-Transmitted Helminthiases in Non-Endemic Implementation Units: A Case Study of Borgu in Northcentral Nigeria

Nigeria remains the most endemic country in sub-Saharan Africa (SSA) for soil-transmitted helminthiases (STH). In line with ongoing monitoring plans, we present findings from a recent analysis of STH epidemiological data in Borgu, one of the non-endemic implementation units for STH in the northcentral region of Nigeria. An overall prevalence of 8.8% was recorded for STH infection, which corresponds to a 51.9% decline from the 18.3% reported in 2013. All the infected participants (36 out of 410) had a low intensity of infection. However, more than two-thirds (69%) of the children do not have access to latrine facilities, and 45% of them walk barefoot. Prevalence was significantly associated with community, age, and parental occupation. About 21-25% reduced odds were reported in some of the study communities, and children whose parents were traders had 20 times lower odds of infection compared to those whose parents were farmers. The ongoing preventive chemotherapy program for lymphatic filariasis in the area could be responsible for the huge reduction in prevalence and intensity estimates for STH. It is therefore important to invest in monitoring transmission dynamics in other non-endemic areas to arrest emerging threats through the provision of complementary interventions including WASH facilities and other health educational tools.

Knowledge and participation in mass drug administration against lymphatic filariasis and soil-transmitted helminth infections among the community members in Dar es Salaam, Tanzania

BACKGROUND

Although the WHO has made an effort to ensure optimal participation of the community in mass drug administration (MDA) against lymphatic filariasis (LF) and soil-transmitted helminth infections (STHIs), studies are still reporting suboptimal coverage. This study assessed the knowledge and participation of the community in MDA against LF and SHTIs in Tanzania to provide updates on its acceptability.

METHODS

A cross-sectional study was conducted in Dar es Salaam from December 2021 to February 2022 among market vendors. The information regarding demographic characteristics, knowledge and participation in MDA was collected using a questionnaire. Statistical Package for Social science version 26 was used for data analysis.

RESULTS

More than half of the participants demonstrated an adequate level of knowledge of LF and STHI, 212 (50.8%) and 267 (64%), respectively. Only 286 (68.5%) reported having heard about MDA against LF and STHIs, out of which 119 (42%) had taken the medication. Of those who disagreed to participate in MDA, 20 (50%) claimed to fear the side effects of the medication.

CONCLUSIONS

This study found that the community has average knowledge and poor participation in MDA against LF and STHIs. Community sensitization is recommended to increase the participation of the community.

Helminthiases in North Korea: a neglected public health challenge

Helminthiasis is a neglected public health challenge threatening North Koreans. However, there is no precise estimate on the burden of helminthiasis in the region. This study therefore reviewed existing literature with the aim of analyzing the current state of helminthiasis among North Koreans, as well as highlighting the difference in the prevalence of helminthiasis between North Korean residents and refugees. All published resources citing helminthiasis among North Koreans were screened through the PubMed and a Korean bibliographic database as of April 2019. Official papers reported by the government and international agencies, as well as reports and books published in North Korea, were reviewed. After removing duplicated government reports, a total of 37 records were screened, and four were determined to be included for review. The total number of study subjects was 621 from the four eligible studies. Forty percent of them were refugees living outside North Korea. Total positive rate of any kind of helminths was 37.7%. Ascaris was the most widespread helminths with a prevalence estimate of 41.1%. The total positive rate of helminthiasis among residents living in North Korea was significantly higher than that among North Korean refugees (47.2% vs. 23.4%, chi-square p-value < 0.001). Poor hygiene, malfunctioning public health infrastructure, and feculent agricultural practices accounted for the spread of helminthiasis. Appropriate strategies and policies should be developed to prevent and alleviate helminthiasis in North Korea.

"Freezing" parasites in pre-Himalayan region, Himachal Pradesh: Experience with mini-FLOTAC

BACKGROUND

Helminths and protozoa infections pose a great burden especially in developing, countries, due to morbidity caused both by acute and chronic infections. Data on distribution of intestinal parasitic infections among the native and expatriates populations in Himachal Pradesh are scarce. The aim of our survey was to analyze the intestinal parasitic burden in communities from Dharamsala, Kangra district, in clinical and public health settings. We also field-tested the mini- FLOTAC, an innovative diagnostic device.

METHODS

Subjects referring to the Tibetan Delek Hospital for abdominal discomfort and all children of the Tibetan Primary School in Dharamsala were screened for intestinal parasitic infections with direct smear, formol-ether concentration (FEC) method and mini-FLOTAC, their clinical history was recorded, and correlations between clinical symptoms and infections analyzed.

RESULTS

152 subjects were screened for intestinal parasites, of which 72 subjects in the outpatients department (OPD) (36 expatriates and 36 natives) and 80 in the school. 60% of schoolchildren and 57% of OPD patients were found positive for any infection, the most represented were protozoa infections (50%), whereas helminthic infections accounted only for 13% and 20% in OPD patients and schoolchildren, respectively. The most prevalent among helminths was Ascaris lumbricoides (11%). Giardia intestinalis was more present among schoolchildren than the OPD patients (20% vs 6%) and E. histolytica/dispar was more prevalent among the OPD patients (42%) than the school children (23%). Correlations were found between nausea and loose or watery stools and parasitic infections, particularly in expatriates, whereas schoolchildren, despite being as infected as adults, were completely asymptomatic. Mini-FLOTAC detected higher number of helminth infections whereas FEC method was more accurate for the diagnosis of protozoa.

CONCLUSIONS

This study presents an accurate snapshot of intestinal parasitic infections in Dharamsala, and their high prevalence calls for more awareness and control measures. Mini-FLOTAC is a promising and simple technique for the diagnosis of helminth infections.

Impact of six rounds of mass drug administration on Brugian filariasis and soil-transmitted helminth infections in eastern Indonesia

BACKGROUND

The lymphatic filarial parasite Brugia timori occurs only in eastern Indonesia where it causes high morbidity. The absence of an animal reservoir, the inefficient transmission by Anopheles mosquitoes and the high sensitivity to DEC/albendazole treatment make this species a prime candidate for elimination by mass drug administration (MDA).

METHODOLOGY/PRINCIPAL FINDINGS

We evaluated the effect of MDA using DEC and albendazole on B. timori and soil transmitted helminths (STH) in a cross-sectional study of a sentinel village on Alor Island annually over a period of 10 years. Pre-MDA the microfilaria (MF) prevalence was 26% and 80% of the residents had filaria-specific IgG4 antibodies. In 2010, 34 months after the 6(th) round of MDA, MF and antibody rates were only 0.17% and 6.4%, respectively. The MDA campaign had also a beneficial effect on STH. Baseline prevalence rates for Ascaris, hookworm and Trichuris were 34%, 28%, and 11%, respectively; these rates were reduced to 27%, 4%, and 2% one year after the 5(th) round of MDA. Unfortunately, STH rates rebounded 34 months after cessation of MDA and approached pre-MDA rates. However, the intensity of STH infection in 2009 was still reduced, and no heavy infections were detected.

CONCLUSIONS/SIGNIFICANCE

MDA with DEC/albendazole has had a major impact on B. timori MF and IgG4 antibody rates, providing a proof of principle that elimination is feasible. We also documented the value of annual DEC/albendazole as a mass de-worming intervention and the importance of continuing some form of STH control after cessation of MDA for filariasis.

Epidemiological assessment of neglected diseases in children: lymphatic filariasis and soil-transmitted helminthiasis

OBJECTIVE

To report the prevalence of lymphatic filariasis and intestinal parasitic infections in school-aged children living in a filariasis endemic area and discuss about the therapeutic regimen adopted in Brazil for the large-scale treatment of filariasis.

METHODS

A cross-sectional study including 508 students aged 5-18 years old, enrolled in public schools within the city of Olinda, Pernambuco. The presence of intestinal parasites was analyzed using the Hoffman, Pons and Janer method on 3 stool samples. The diagnosis of filarial infection was performed using the rapid immunochromatographic technique (ICT) for the antigen, and the polycarbonate membrane filtration for the presence of microfilariae. Descriptive statistics of the data was performed using EpiInfo version 7.

RESULTS

The prevalence of filariasis was 13.8% by ICT and 1.2% by microfilaraemia, while intestinal parasites were detected in 64.2% of cases. Concurrent diagnosis of filariasis and intestinal parasites was 9.4%, while 31.5% of students were parasite-free. Among individuals with intestinal parasites, 55% had one parasite and 45% had more than one parasite. Geohelminths occurred in 72.5% of the parasited individuals. In the group with filarial infection the prevalence of soil-transmitted helminthiasis was 54.5%.

CONCLUSIONS

The simultaneous diagnosis of filariasis and intestinal parasites as well as the high frequency of geohelminths justify the need to reevaluate the treatment strategy used in the Brazilian filariasis large-scale treatment program.

Exposure to hookworms in patients with Crohn's disease: a case-control study

BACKGROUND

Helminths have been used to inhibit intestinal inflammation in patients with Crohn's disease.

AIM

This study was undertaken to determine if there is a protective association of prior hookworm infection with Crohn's disease, in a region where there is epidemiological transition from parasitic and infectious diseases to increased auto-inflammatory diseases.

METHODS

Hookworm exposure was assessed by peripheral blood mononuclear cell (PBMC) activation by hookworm antigens in 78 patients with Crohn's disease and 75 healthy control participants. The change in proportion of T cells exhibiting CD69 after exposure to crude hookworm antigens was measured. Interferon-γ ELISPOT response to a panel of six recombinant hookworm antigens was analysed.

RESULTS

Patients with Crohn's disease were more often from an urban background (P=0.005) compared to controls, while their socioeconomic status was not significantly different. T cell activation (increase in CD3(+) CD69(+) population) by hookworm antigen was significantly higher in controls compared to Crohn's disease patients (P=0.017), while activation by the nonspecific mitogen phytohemagglutinin was similar in both groups. Circulating T memory cells (CD3(+) CD45RO(+)) after exposure to hookworm antigens were not significantly different between the two groups. Mirroring these changes, interferon-γ ELISPOT responses to hookworm antigens were seen in 36 of 75 controls compared to 20 of 78 Crohn's disease patients (Fisher's exact P=0.005). Multivariate analysis indicated that CD3CD69 shifts (P=0.019), ELISPOT reactivity (P=0.039) and place of residence (P=0.024) were all independently associated with Crohn's disease.

CONCLUSION

The inverse association between Crohn's disease and hookworm antigen reactivity is consistent with the hygiene hypothesis, but requires further exploration.

Soil-transmitted helminths of humans in Southeast Asia--towards integrated control

Soil-transmitted helminths (STHs) pose significant public health challenges in many countries of Southeast Asia (SEA). Overall, approximately one-third of the world's cases of ascariasis, trichuriasis, and hookworm disease occur in the 11 major SEA countries. Various countries are at different stages in their response to controlling these diseases. For instance, in Malaysia and Thailand, the major burden of disease is confined to rural/remote, indigenous and/or refugee populations. In countries, such as Cambodia, Lao People's Democratic Republic and Vietnam, the burden remains high, although extensive deworming programmes are underway and are yielding encouraging results. The present chapter reviews the current status of STH infections in SEA, identifies knowledge gaps and offers a perspective on the development of improved, integrated surveillance and control in this geographical region. It indicates that advances in our understanding of the epidemiology of these parasites, through the strategic use of molecular and predictive (e.g. geographical information systems (GIS) and remote sensing (RS)) technologies, could readily underpin future research and control programmes. It is hoped that the gradual move towards integrated treatment/control programmes will assist substantially in decreasing the chronic disease burden linked to STHs, thus increasing human health and welfare, and supporting socio-economic growth and development in SEA countries.

Prevention of lymphatic filariasis with insecticide-treated bednets in Cambodia

Potential risk factors for lymphatic filariasis (LF), including the failure to use insecticide-treated bednets (ITN), were studied in four north-eastern provinces of Cambodia, using 43 cases of LF and 248 apparently healthy controls who were matched with the cases in terms of age (+/-5 years), gender and village. The results of a univariate matched analysis indicated that lack of ITN [odds ratio (OR)=20.1; 95% confidence interval (CI)=2.2-182.4; P=0.008] and frequent overnight stays in forests or paddy fields outside the village (OR=3.6; CI=1.3-10.0; P=0.012) were the most important risk factors. In a multivariate matched analysis, frequent overnight stays outside the village combined with bednet use showed a clear dose-response relationship, with untreated nets offering significant protection during such stays but ITN offering significantly better protection. Even if villagers used ITN during such stays, they were significantly more likely to develop LF than villagers who did not travel (OR=5.0; CI=1.5-16.3; P=0.008), and if they used untreated or no nets while away they were even more likely than the non-travellers to develop the disease (OR=1413; CI=28.0-71,189; P<0.001). Taken together, these results provide further evidence for the importance of bednet use and their impregnation in the prevention of LF. At least in north-eastern Cambodia, the use of bednets and, preferably, ITN is particularly important during overnight stays outside the home village. In areas where LF is endemic, the sustained distribution of insecticide-treated bednets or hammock nets appears to be a very good idea.