Helminth diseases

Medical parasitology is crucial in the diagnosis and treatment of human infections. Helminths are important parasites that plague human beings and cause various potentially fatal diseases. The term helminth is derived from the Greek word for worms. Therefore, helminths can be defined as parasitic worms. They are the most prevalent human infectious agents in developing countries. There are multiple categories of helminth infections. Clinical evidence links these parasites to different helminth diseases, including ascariasis and schistosomiasis. These diseases may be transmitted through worms in the soil, contaminated food, or water. In-depth research into medical helminthology led to improved treatment against parasitic infections. 

Classification of helminths

The classification of these worms centres on those that are clinically relevant. They are separated into groups according to their morphological characteristics and host organs. The main species include the nematodes, cestodes, and trematodes.

– Nematodes

They are also called roundworms due to their cylindrical external shape observed in their larval and adult forms. They can exist as parasites or inhabit fresh waters, soils, and marine ecosystems as free microorganisms.

They invade the human body as parasites and occupy intestinal and extraintestinal sites. The common extraintestinal sites include the respiratory and circulatory systems. Some worms that fall into this category include hookworms, threadworms, whipworms, and lungworms. Most intestinal worms and filarial worms belong to this species.

– Trematodes

These worms are known as flukes or flatworms. They can be ectoparasites or endoparasites. Depending on the species, trematodes invade one or more hosts. They have a flattened and leaflike external shape with muscular suckers on their ventral surface. Their bodies are lined with hooks and spines for attachment. Human parasitic trematodes are found in the blood, intestines, and liver. Examples include schistosomes.

– Cestodes

This parasitic group of worms is referred to as tapeworms. They are internal parasites that invade the liver and digestive tract. Some tapeworms attach a single host throughout their life cycle. However, others exist in several intermediate hosts before occurring in a definitive host to mature. Human beings are their definitive hosts. 

Affected organs in helminth diseases

During helminth infection, flukes invade specific parts of the body. The lungs are a common sight for the fluke known as Paragonimus westermani. Clinically relevant blood flukes include Schistosoma mansoni, Schistosoma japonicum, and Schistosoma haematobium. The species Schistosoma japonicum is a major parasite found in human blood. Furthermore, examples of liver flukes include Fasciola hepatica and Clonorchis Sinensis. Flukes commonly found in the intestines are Fasciolopsis buski and Mettgonimus yokagawi. 

Human helminth diseases

Helminth infections are generally termed helminthiasis in human beings. The most prevalent helminthiasis is ascariasis. Contaminated water sources, soil, and food facilitate the transmission of parasitic worms. There have been great advancements in the control and treatment of helminthiasis.

Ascariasis

The roundworm Ascaris lumbricoides cause this condition. The roundworms invade the intestines as their larvae and adult forms. Infection with these worms may go unnoticed as most patients lack symptoms. However, when left unchecked, their population increases and the person experiences abdominal symptoms. 

Heavy worm infection is characterised by intestinal obstruction and perforations. Ascaris species can also migrate to other body parts, including the lungs and liver. Some patients have liver abscesses, pancreatitis, and appendicitis.

Hookworm infections

Hookworm is caused by Ancylostoma duodenale, a common infection in tropical areas. Many patients are asymptomatic. However, some patients present with abdominal pain, nausea, vomiting, and bloody diarrhoea. They also report an itchy sensation at the site of penetration. 

The unmitigated infection could lead to iron deficiency anaemia and hypoalbuminemia. 

Its diagnosis involves the analysis of blood tests, stool cultures, and faecal microscopy. The treatment options available include albendazole, mebendazole, and ivermectin. These drugs are contraindicated in pregnant and breastfeeding women.

Schistosomiasis

The etiological agent responsible for this disease is the Schistosoma species. The member organisms include S. japonicum, S. mansoni, S. intercalated, S. mekongi, and S. haematobium. Schistosomiasis is also referred to as bilharzia. This infection predominantly occurs in freshwater areas. 

Initially, infected individuals are asymptomatic due to negligible worm count. However, further progression leads to acute infection characterised by an itchy rash, sudden onset of fever, angioedema, dry cough, diarrhoea, abdominal pain, and headache. Acute schistosomiasis syndrome resolves itself spontaneously within a few weeks. On the other hand, chronic bilharzia has severe effects on the body.

Conclusion

Medical helminthology analyses the different worms and their clinical relevance. Multiple helminth species invade the body systems and cause infections. Helminth diseases can also be referred to as helminthiasis. The body systems commonly affected by these parasitic worms include the respiratory, gastrointestinal, and circulatory systems. Flukes are commonly found in the liver, blood, and intestines. Here, they reproduce and multiply quickly. After initial infection, patients may be asymptomatic as very few worms are in their bodies. However, unresolved infections lead to a high population of parasitic worms that damage the internal organs. The diagnosis of helminth infection requires blood tests and stool samples.