¹Department of Zoology, Govt Post Graduate College Fatehabad Agra, Uttar Pradesh

²Department of Botany, Govt Post Graduate College Fatehabad Agra, Uttar Pradesh

Corresponding Author eMail: shilpy.shilpy@gmail.com

Article Publishing History

INTRODUCTION

The word ‘helminth’ is a general term, which is often used to convey one or the other form of parasitic infections. In academic and research world, it is a broad term encompassing all known flatworms and roundworms. Helminths are metazoan animals with multi-cellular arrangement and a body which is like a tube within tube. Outer tube is a tough cuticular skin and the inner tube contains all the body parts including digestive and reproductive systems. These animals exhibit bilateral symmetry, triploblastic in terms of muscular arrangement and important pseudocoelomatic creatures of the nature (Okwa, 2020). While majority of helminths are free-living in aquatic and terrestrial environment, few are parasites in human and plants. It is the parasitic forms which have received much attention due to the diseases they cause in both humans as well as in plants (Elton, 2020, Combes, 2020).

Helminths are very special compared to other parasites in nature (Rapin & Harris, 2018).. Their development is quite slow compared to other infectious pathogens. Diseases caused by helminths have slow onset but are chronic in nature (Mutapi et al., 2017). Although mostly go as asymptomatic, helminths infection cause severe economic damage worldwide and are associated with high level of morbidity and mortality (Krolewiecki & Nutman, 2019). All human parasitic nematodes have similar life cycle with certain notable differences (Ancell & Pires-daSilva, 2017, Jex,  et al., 2019). They demonstrate a well developed sexual dimorphism. Females of the parasitic nematode produces large number of eggs that after hatching pass through four larval stages and turn into an adult (Chaudhuri et al., 2011). Understanding the life-cycle of animal parasitic nematode is essential to identify the vulnerable stages which can be targeted for its management. Common route of transmission adopted by nematode parasite includes faecal-oral transmission, transdermal transmission, vector-borne transmission and predator-prey transmission (Furtado et al., 2020).

Infection by parasitic nematodes is a common problem throughout the world. Their enormous distribution and infections in human population can be understood by a fact that in year 1946, it was estimated that a population of 2.2 billion at that time had 2.3 billion nematode infections. Each human being was infected by more than one nematode (Becker et al., 2018). Their impact on the lives of human and animals is very drastic and frightening. Nematode infections are a cause of serious problem in the developing world­ where intestinal infections are the most frequent ones. Common intestinal nematodes from the developing world are Ascaris lumbricoides, Trichuris trichiura and Strongyloides stercoralis (Table-1). Important nematodes of veterinary importance are Ostertagia ostertagi, Cooperia oncophora, Teladorsagia circumcincta, Haemonchus contortus, Dictyocaulus viviparous. Details of each of these nematodes are listed (Table-2).

From human perspective, these three nematodes account for three-quarter of all infections (Freeman et al., 2019). Global atlas on nematode infection is complied based on the findings of several research groups. Throughout the world, more than half of the population is affected by nematode infections. Even in the presence of modern medical aids, incidences of nematode infections are continuously increasing mostly from the developing world (Van Den Hoogen et al., 2019). A number of factors are responsible for this increase, which includes lack of awareness about proper sanitation and health related issues. Treatment of the nematode infection depends mostly on chemical based medicines (Werkman et al., 2020). Recently, the progresses in research have led to discoveries of plant based antihelmintic treatments (Liu et al., 2020, Zajíčková et al., 2020).

In order to make informed policy decisions and plan better management strategies, detailed and meaningful data is required. This review presents the insight and highlights the impact of the nematode infection on human and animals. Progress in the field of parasitic nematodes has not seen much pace compared to other fields. Major reason for this slow growth had been the biology of these animals. These animals live deep inside their host, are bio-trophic in nature, have long life-cycles, are difficult to culture in laboratory outside their host etc. Through this review an attempt has been made to summarize the important parasitic helminths which are responsible for significant morbidity in both humans as well as animals. In order to summarize the details, we have looked in to various publication, looked in to metadata presented, searched important search engines and presented the updated details.

Reason Behind The Ignorance

There are around 342 species of nematode that infect human beings (Laurimaa et al., 2016). Nematode infections have increased with increasing human population globally (Sorobetea et al., 2018). Published data suggests that there are significant numbers of infections reported worldwide. Out of the 3500 million infections worldwide, there are 450 million individual who require serious medical attention. As per recorded data, more than 125000 deaths occur every year due to nematode infections, particularly by Ancyclostoma (Coulibaly et al., 2019). The reason behind ignorance of nematode infection is primarily due to their asymptomatic and non fatal nature compared to the infections cause by protozoan parasites especially malaria, which receives so much public attention and huge research funding (Rückerl, 2020). Most common symptoms associated with parasitic nematodes infection in humans include abdominal pain, diarrhoea, malnutrition, and anaemia (Tamarozzi et al., 2019). In certain case of Trichuris infection, cognitive function is impaired to some extent, due to secondary infections by opportunistic pathogens etc. Details about the mechanism of infection, adverse effect of infection and the economical impact due to these infections can be gained from several excellent reviews (Jourdan et al., 2018,  Wright et al., 2018, Ramlal et al., 2019 Norman et al., 2020).

Problem in Management of Nematode Infections

As mentioned earlier that good level of personal hygiene, proper sanitation and health-related education is a must for creating awareness against these infections. Based on the published reports, only personal hygiene helps in reducing the rising cases of nematode infections throughout the globe (World Health Organization, 2018). There are various challenges associated with management of nematode infections. Since the problem of nematode infection is a global problem, its management becomes more complex because of varying level of environmental, social and economic factors across different countries. Scientists have pointed out that it is next to impossible to get our world free from nematode infections, but certainly we should be able to manage it. In order to control of limit the infections caused by helminths, focus must be on reducing contact based transmission of parasites as this strategy will help in reducing the risk of spreading further infections (World Health Organization, 2019).

Control Methods

The treatment and control of animal parasitic nematode infection is primarily dependent on anthelmintic drugs. Benzimidazoles group of medicines like albendazole and mebendazole, imidazothiazoles group of medicines such as levamisole and pyrantel are common chemical anthelmintic drugs recommended by various agencies (Enejo & Suleiman, 2017; Gandasegui et al., 2020). Thiabendazole, which is structurally related to albendazole and mebendazole, is used widely for the treatment of several nematodes of cattle, horses, and sheep (Legarda-Ceballos et al., 2016). Dithiazanine is another nematode anthelmintic used in veterinary medicine; it is effective against heartworms and threadworms. Diethylcarbamazine is the drug of choice for treatment of filariasis caused by a parasitic nematode, Wuchereria bancrofti throughout the globe (McCarthy & Moore, 2015, Misra-Bhattacharya & Shahab, 2018). Though, a polytherapy treatment that includes ivermectin with diethylcarbamazine or albendazole is more effective than either drug alone. Macrocyclic lactones group of medicines are an important class of anthelmintics for the control of nematode parasites and some ectoparasites in livestock, companion animals and in humans (Prichard  & Geary 2019).

Similarly, pyrantel pamoate is effective against Ancyclostoma. As part of integrated pest management, scientists are looking beyond the reliance only on chemical based anthelmintics for treatment of parasitic nematode infections. Certain plant metabolites have been also evaluated for controlling nematode diseases of humans (Athanasiadou et al., 2007, Punetha et al., 2020). Use of plant based products for controlling livestock nematodes has also been tried. Plant based products offer alternative methods of controlling animal parasitic nematodes (Behera & Bhatnagar, 2018, Garcia-Bustos et al., 2019).

Table 1. List of important nematodes causing significant infection in humans

S.N	Name of the parasite	Common Name	Clinical symptoms	Transmission	Distribution	Number of infected worldwide	References
1.	Ascaris lumbricoides	Roundworm	Abdominal pain, diarrhoea, malnutrition	Ingestion of eggs	Worldwide	807-1,121 Million	(Shah and Shahidullah, 2018)
2.	Ancylostoma duodenale	Hookworm	Cough, dyspnea and Hemoptysis	Contaminated soil	Worldwide	576-740 Million	(Giramkar, 2020)
3.	Trichuris trichiura	Whipworms	Abdominal pain, unexpected weight loss	Contaminated soil and food	Worldwide	604-795 Million	( Else. et al., 2020)
4.	Onchocerca volvulus	River Blindness worm	Skin and lymph node inflammation	Repeated bites by black flies	Sub-Saharan Africa	187 Million	(Otabil. et al., 2019)
5.	Wuchereria bancrofti	Filarial worm	Lymphedema,	Through the bite of an infectious mosquito	Africa and India	893 Million	(Zulch. et al., 2020)
6.	Brugia malayi	Filarial worm	Ulceration of the affected lymph node	Mosquito vector	South-east Asia	120 Million	(Liu et al, 2018)
7.	Dracunculus medinensis	Guinea worm	Nausea, vomiting, Blisters.	By drinking unfiltered water	Remote areas of Africa	3.5 Million	(Robert L, 2019)
8.	Enterobius vermicularis	Pin worm	Perianal pruritus	Ingestion of Infectious eggs	Worldwide	1.0 Billion	(Fan et al., 2019)

Table 2. List of important nematodes from veterinary perspective

S.No.	Name of the parasite	Host	Distribution	References
1.	Ostertagia ostertagi	Gastrointestinal nematodes (GINs) of grazing cattle	Worldwide	(Singh B. et al., 2019)
2.	Cooperia oncophora	Gastrointestinal nematodes (GINs) of grazing cattle	Worldwide	(Candy et al., 2018)
3.	Teladorsagia circumcincta	Small ruminants such as sheep	Worldwide	(Stear. et al., 2019)
4.	Haemonchus contortus	Attached to the abomasum of ruminants (sheep, goats and cattle)	Worldwide	(Brik. et al., 2019)
5.	Dictyocaulus viviparous	In the bronchial tree of horses, sheep, goats, deer, and cattle	Worldwide	(Claerebout & Geldhof 2020)

Socio-Ecomonic Impact Of Helminths Infection

Significant morbidity and mortality takes places due to infections by helminths (Feasey et al., 2010, Gadoth, 2019). Many regions of the world, especially the developing world are facing severe problem due to the infections caused by helminths (De Rycker et al., 2018). Unhygienic living conditions and non-availability of safe drinking water is directly linked to the development and proliferation of these diseases. In essence, parasitic diseases caused by helminths are considered to be the diseases of poor and exhibit significant socio-economic impact on the society (Lindahl & Grace, 2015). The severity of the impact can be felt through the disease burden both in human as well as in livestock. Developing countries are particularly are at the risk of this uninvited socio-economic burden due to large population, poor hygienic conditions and lack of awareness (Gizaw et al, 2020).

Significant progress has been made by agencies such as United Nations development programme and world health organization in assessing the socio-economic impact of these tropical diseases (Bangert et al., 2017). With the aid from these agencies, global disease burden can be minimized either through eradication or controlling specific diseases. All such project will surely involve the cost effectiveness or cost benefit. However, the information gathered through these special programmes is helping in decision making in respect to treatment and control. Results obtained through survey studies and clinical approaches are used at national level for making key decisions about the socio-economic consequences of diseases caused by helminths and their control. More research on prevalence, its distribution and infection mechanism is required in order to reduce the burden of parasitic diseases and to plan initiatives for its prevention and control (Redekop et al., 2017). Helminths cause significant economic losses worldwide. Due to helminths infection in cattle, overall loss has been estimated to be $ 50.67 per animal per year, which in terms of percentage, is 17.94% annually (Rashid et al., 2019). Data on economic losses due to helminths infection in humans is not available directly but the seriousness can be inferred from the fact that approximately 1.0 billion people are infected by these helminths annually (Gordon et al., 2017, Sherman, 2018).

CONCLUSION

Nematode cause considerable problems in both human as well as in domestic and veterinary animals. These infections not only cause significant deleterious effect on the life of their hosts but also cause huge monetary loss. Though impact of the diseases could be dramatically reduced by improved sanitation for humans and pasture control in domestic animals, such methods are insufficient to eradicate these parasites. In the absence of vaccines, use of chemical based compounds is the sole method to ease disease symptoms, control infection and reduce transmission. Irrespective of having WHO recommended global standard anthelmintics drugs available for treatment of nematode infections, cases of nematode infection are on the rise. The intensive and indiscriminate use of these drugs has led to widespread resistance to all current anthelmintics.

Continuous search for new anthelmintics agents and identification of new drug targets is required to overcome or prevent the issue of drug resistance.  Many plant based naturally occurring compounds have been reported to possess anti-nematode potential. There is also need for well trained and skilled professionals who are capable of integrating and implementing new technologies into their countries. As the problem is global, several health agencies of various countries need to work in collaborated and coordinated manner in order to combat the disease. There is an urgent need for viable, safe and sustainable control strategies that requires an integrated approach incorporating environmental management, and includes a combination drug therapy so as to minimize the chances of parasite adaptation.

Authors Contributions

Both the authors in this manuscript have made substantial contributions towards conception, design, acquisition of data, analysis and interpretation of the data, participated in drafting the manuscript and revising it critically for important intellectual content. Both the authors have seen the final version of the manuscript and approved the same.

ACKNOWLEDGEMENTS

Authors of this manuscript would like to acknowledge their colleagues for providing suggestions and useful insight during the preparation of this manuscript.

Competing Interests

The authors declare that there are no competing interests.

REFERENCES

Ancell, H., & Pires-daSilva, A. (2017, October). Sex-specific lifespan and its evolution in nematodes. In Seminars in cell & developmental biology (Vol. 70, pp. 122-129). Academic Press.

Athanasiadou, S., Githiori, J. and Kyriazakis, I. (2007). Medicinal plants for helminth parasite control: facts and fiction. Animal, 1(9), pp.1392-1400.

Bangert, M., Molyneux, D. H., Lindsay, S. W., Fitzpatrick, C., & Engels, D. (2017). The cross-cutting contribution of the end of neglected tropical diseases to the sustainable development goals. Infectious diseases of poverty, 6(1), 73.

Becker, S. L., Liwanag, H. J., Snyder, J. S., Akogun, O., Belizario Jr, V., Freeman, M. C. & Levecke, B. (2018). Toward the 2020 goal of soil-transmitted helminthiasis control and elimination. PLoS neglected tropical diseases, 12(8), e0006606.

Behera, D. R., & Bhatnagar, S. (2018). Filariasis: Role of medicinal plant in lymphatic filariasis. International Journal of Herbal Medicine, 6(1), 40-46.

Brik, K., Hassouni, T., Elkharrim, K. and Belghyti, D. (2019). A survey of Haemonchus contortus parasite of sheep from Gharb plain, Morocco. Parasite epidemiology and control, p.e00094.

Candy, P. M., Waghorn, T. S., Miller, C. M., Ganesh, S., & Leathwick, D. M. (2018). The effect on liveweight gain of using anthelmintics with incomplete efficacy against resistant Cooperia oncophora in cattle. Veterinary parasitology, 251, 56-62.

Chaudhuri, J., Kache, V., & Pires-daSilva, A. (2011). Regulation of sexual plasticity in a nematode that produces males, females, and hermaphrodites. Current Biology, 21(18), 1548-1551.

Claerebout, E., & Geldhof, P. (2020). Helminth vaccines in ruminants: from development to application. Veterinary Clinics: Food Animal Practice, 36(1), 159-171.

Combes, C. (2020). The art of being a parasite. University of Chicago Press.

Coulibaly JT, Hiroshige N, N’Gbesso YK, et al. Efficacy and safety of ascending dosages of tribendimidine against hookworm infections in children: A randomized controlled trial. Clin Infect Dis 2019; 69:845.

De Rycker, M., Baragana, B., Duce, S. L., & Gilbert, I. H. (2018). Challenges and recent progress in drug discovery for tropical diseases. Nature, 559(7715), 498-506.

Else, K. J., Keiser, J., Holland, C. V., Grencis, R. K., Sattelle, D. B., Fujiwara, R. T. & Cooper, P. J. (2020). Whipworm and roundworm infections. Nature Reviews Disease Primers, 6(1), 1-23.

Elton, C. S. (2020). The ecology of invasions by animals and plants. Springer Nature.

Enejoh, O.S. and Suleiman, M.M. (2017). Anthelmintics and their application in veterinary medicine. Res. Med. Eng. Sci, 2.

Fan, C.K., Chuang, T.W., Huang, Y.C., Yin, A.W., Chou, C.M., Hsu, Y.T., Kios, R., Hsu, S.L., Wang, Y.T., Wu, M.S. and Lin, J.W. (2019). Enterobius vermicularis infection: prevalence and risk factors among preschool children in kindergarten in the capital area, Republic of the Marshall Islands. BMC infectious diseases, 19(1), p.536.

Feasey, N., Wansbrough-Jones, M., Mabey, D. C., & Solomon, A. W. (2010). Neglected tropical diseases. British medical bulletin, 93(1), 179-200.

Freeman, M. C., Akogun, O., Belizario Jr, V., Brooker, S. J., Gyorkos, T. W., Imtiaz, R., … & Utzinger, J. (2019). Challenges and opportunities for control and elimination of soil-transmitted helminth infection beyond 2020. PLoS neglected tropical diseases, 13(4), e0007201.

Furtado, L. F. V., de Oliveira Dias, L. T., de Oliveira Rodrigues, T., da Silva, V. J., de Oliveira, V. N. G. M., & Rabelo, É. M. L. (2020). Egg genotyping reveals the possibility of patent Ancylostoma caninum infection in human intestine. Scientific reports, 10(1), 1-7.

Gadoth, A. (2019). Helminth infection and treatment among pregnant women in the Democratic Republic of Congo: An examination of associated risk factors, co-morbidities, and birth outcomes (Doctoral dissertation, UCLA).

Gandasegui, J., Martínez-Valladares, M., Grau-Pujol, B., Krolewiecki, A. J., Balaña-Fouce, R., Gelaye, W. & Stopping Transmission Of intestinal Parasites (STOP) project consortium. (2020). Role of DNA-detection–based tools for monitoring the soil-transmitted helminth treatment response in drug-efficacy trials. PLoS Neglected Tropical Diseases, 14(2), e0007931.

Garcia-Bustos, J. F., Sleebs, B. E., & Gasser, R. B. (2019). An appraisal of natural products active against parasitic nematodes of animals. Parasites & vectors, 12(1), 1-22.

Giramkar, S. V. (2020). Phylum Aschelminthes.  Paper-1, ZO-121.

Gizaw, Z., Addisu, A., Gebrehiwot, M. (2020) Socioeconomic Predictors of Intestinal Parasitic Infections Among Under-Five Children in Rural Dembiya, Northwest Ethiopia: A Community-Based Cross-sectional Study. Environmental Health Insights, 13(1).

Gordon, C.A., Kurscheid, J., Jones, M.K., Gray, D.J. and McManus, D.P. ( 2017). Soil-transmitted helminths in tropical Australia and Asia. Tropical medicine and infectious disease, 2(4), p.56.

Jex, A. R., Gasser, R. B., & Schwarz, E. M. (2019). Transcriptomic resources for parasitic nematodes of veterinary importance. Trends in parasitology, 35(1), 72-84.

Jourdan, P. M., Lamberton, P. H., Fenwick, A., & Addiss, D. G. (2018). Soil-transmitted helminth infections. The Lancet, 391(10117), 252-265.

Krolewiecki, A., & Nutman, T. B. (2019). Strongyloidiasis: a neglected tropical disease. Infectious Disease Clinics, 33(1), 135-151.

Laurimaa, L., Süld, K., Davison, J., Moks, E., Valdmann, H., & Saarma, U. (2016). Alien species and their zoonotic parasites in native and introduced ranges: the raccoon dog example. Veterinary parasitology, 219, 24-33.

Legarda-Ceballos, A. L., Rojas-Caraballo, J., López-Abán, J., Ruano, A. L., Yepes, E., Gajate, C. & Muro, A. (2016). The alkylphospholipid edelfosine shows activity against Strongyloides venezuelensis and induces apoptosis-like cell death. Acta tropica, 162, 180-187.

Lindahl, J. F., & Grace, D. (2015). The consequences of human actions on risks for infectious diseases: a review. Infection ecology & epidemiology, 5(1), 30048.

Liu C, Mhashilkar AS, Chabanon J, Xu S, Lustigman S, et al. (2018) Development of a toolkit for piggyBac-mediated integrative transfection of the human filarial parasite Brugia malayi. PLoS Negl Trop Dis 12: e0006509.

Liu, M., Panda, S. K., & Luyten, W. (2020). Plant-Based Natural Products for the Discovery and Development of Novel Anthelmintics against Nematodes. Biomolecules, 10(3), 426.

McCarthy, J. S., & Moore, T. A. (2015). Drugs for helminths. Mandel, Douglas and Bennett’s Principles and Practice of Infectious Diseases. 8th ed. Philadelphia: Saunders.

Misra-Bhattacharya, S., & Shahab, M. (2018). Progress in the Treatment and Control of Lymphatic Filariasis. In Lymphatic Filariasis (pp. 47-58). Springer, Singapore.

Mutapi, F., Maizels, R., Fenwick, A., & Woolhouse, M. (2017). Human schistosomiasis in the post mass drug administration era. The Lancet Infectious Diseases, 17(2), e42-e48.

Norman, F. F., Chamorro, S., Comeche, B., Pérez-Molina, J. A., & López-Vélez, R. (2020). Update on the major imported helminth infections in travellers and migrants. Future Microbiology, 15(6), 437-444.

Okwa, O. O. (2020). Introductory Chapter: Helminthes Diversity-Focus on Nematodes. In Helminthiasis. Intech Open.

Otabil, K.B., Gyasi, S.F., Awuah, E., Obeng-Ofori, D., Atta-Nyarko, R.J., Andoh, D., Conduah, B., Agbenyikey, L., Aseidu, P., Ankrah, C.B. and Nuhu, A.R. (2019). Prevalence of onchocerciasis and associated clinical manifestations in selected hypoendemic communities in Ghana following long-term administration of ivermectin. BMC infectious diseases, 19(1), p.431.

Prichard R.K., Geary T.G. (2019) Perspectives on the utility of moxidectin for the control of parasitic nematodes in the face of developing anthelmintic resistance.  International Journal for Parasitology: Drugs and Drug Resistance, 10 , pp. 69-83.

Punetha, H., Saif, N. S., & Dinesh, P. (2020). Glucosinolates in Oilseed Brassica: Neutraceuticals with Tremendous Health Benefits. Biotech Today: An International Journal of Biological Sciences, 9(2), 26-32.

Ramlal, P. S., Stenström, T. A., Munien, S., Amoah, I. D., & Buckley, C. A. (2019). Relationships between shared sanitation facilities and diarrhoeal and soil-transmitted helminth infections: an analytical review. Journal of Water, Sanitation and Hygiene for Development, 9(2), 198-209.

Rapin, A., & Harris, N. L. (2018). Helminth–bacterial interactions: cause and consequence. Trends in immunology, 39(9), 724-733.

Rashid, M., Rashid, M.I., Akbar, H., Ahmad, L., Hassan, M.A., Ashraf, K., Saeed, K. and Gharbi, M. (2019). A systematic review on modelling approaches for economic losses studies caused by parasites and their associated diseases in cattle. Parasitology, 146(2), pp.129-141.

Redekop, W. K., Lenk, E. J., Luyendijk, M., Fitzpatrick, C., Niessen, L., Stolk, W. A. & Richardus, J. H. (2017). The socioeconomic benefit to individuals of achieving the 2020 targets for five preventive chemotherapy neglected tropical diseases. PLoS neglected tropical diseases, 11(1), e0005289.

Roberts L. Battle to wipe out debilitating Guinea worm parasite hits 10 year delay. Nature 2019; 574: 157–58.

Rückerl, D. (2020). Macrophages and parasites: mortal enemies or partners in crime?. Parasite Immunology, e12725.

Shah, J. and Shahidullah, A. (2018). Ascaris lumbricoides: a startling discovery during screening colonoscopy. Case reports in gastroenterology, 12(2), pp.224-229.

Sherman, A. (2018). Medical Parasitology. Scientific e-Resources.

Singh, B., Flampouri, E., & Dempsey, E. (2019). Electrochemical enzyme-linked immunosorbent assay (e-ELISA) for parasitic nematode Ostertagia ostertagi (brown stomach worm) infections in dairy cattle. Analyst, 144(19), 5748-5754.

Sorobetea, D., Svensson-Frej, M., & Grencis, R. (2018). Immunity to gastrointestinal nematode infections. Mucosal Immunology, 11(2), 304-315.

Stear, M., Piedrafita, D., Sloan, S., Alenizi, D., Cairns, C. and Jenvey, C. (2019). Teladorsagia circumcincta. WikiJournal of Science, 2(1), p.1.

Tamarozzi, F., Martello, E., Giorli, G., Fittipaldo, A., Staffolani, S., Montresor, A. & Buonfrate, D. (2019). Morbidity associated with chronic Strongyloides stercoralis infection: a systematic review and meta-analysis. The American journal of tropical medicine and hygiene, 100(6), 1305-1311.

Van Den Hoogen, J., Geisen, S., Routh, D., Ferris, H., Traunspurger, W., Wardle, D. A  & Bardgett, R. D. (2019). Soil nematode abundance and functional group composition at a global scale. Nature, 572(7768), 194-198.

Werkman, M., Wright, J. E., Truscott, J. E., Oswald, W. E., Halliday, K. E., Papaiakovou, M., & Anderson, R. M. (2020). The impact of community-wide, mass drug administration on aggregation of soil-transmitted helminth infection in human host populations. Parasites & Vectors, 13(1), 1-12.

WHO (2019) Global update on implementation of preventive chemotherapy against neglected tropical diseases in 2018. Weekly Epi Record 38: 425–440.

WHO (2018). Managing epidemics: key facts about major deadly diseases. World Health Organization.

Wright, J. E., Werkman, M., Dunn, J. C., & Anderson, R. M. (2018). Current epidemiological evidence for predisposition to high or low intensity human helminth infection: a systematic review. Parasites & vectors, 11(1), 65.

Zajíčková, M., Nguyen, L. T., Skálová, L., Stuchlíková, L. R., & Matoušková, P. (2020). Anthelmintics in the future: current trends in the discovery and development of new drugs against gastrointestinal nematodes. Drug Discovery Today, 25(2), 430-437.

Zulch, M. F., Pilotte, N., Grant, J. R., Minetti, C., Reimer, L. J., & Williams, S. A. (2020). Selection and exploitation of prevalent, tandemly repeated genomic targets for improved real-time PCR-based detection of Wuchereria bancrofti and Plasmodium falciparum in mosquitoes. PloS one, 15(5), e0232325.