Medical parasitology is the branch of science that deals with parasites which infect humans, causing various diseases and public health challenges. A parasite is an organism that lives on or within another living organism, known as the host, at whose expense it obtains nutrients and shelter. In the context of healthcare in Nigeria, understanding parasitology is vital because parasitic infections contribute significantly to maternal morbidity, childhood malnutrition, and general hospital admissions.
Parasites range from microscopic single-celled protozoa to large multicellular helminths like tapeworms. They have evolved complex survival mechanisms to evade the human immune system, often altering their surface proteins or hiding inside host cells. Midwives encounter these organisms frequently during antenatal care, where infections like malaria or hookworm directly threaten the wellbeing of both mother and baby.
The interaction between humans and microorganisms involves several ecological relationships. Symbiosis broadly refers to any close and long-term biological interaction between two different biological organisms. This relationship takes different forms depending on whether the organisms benefit, harm, or remain unaffected.
Medical parasites are broadly categorized into two major groups based on their cellular structure and size: protozoa and helminths. Ectoparasites, which live on the outer surface of the skin, form a third important clinical category.
| Category | Description | Common Example |
|---|---|---|
| Protozoa | Microscopic, single-celled eukaryotes | *Plasmodium* species |
| Helminths | Multicellular, macroscopic worms | *Ascaris lumbricoides* |
| Ectoparasites | Organisms residing on the skin surface | Sarcoptes scabiei |
Understanding how parasites move from one host to another helps in planning effective prevention strategies. Some parasites complete their development within a single host, while others require multiple distinct hosts to finish their life cycle.
Direct life cycles involve only one definitive host. The parasite is shed through faeces or body fluids and infects a new host directly, often through contaminated soil, hands, or water. *Ascaris lumbricoides* spreads this way when unwashed food carries infective eggs.
Indirect life cycles require an intermediate host in addition to the definitive host where sexual reproduction occurs. For instance, *Plasmodium* relies on the female Anopheles mosquito as a vector and intermediate host before transmission to humans.
Midwives and nurses in Nigeria encounter several endemic parasitic infections during routine clinical duties. Malaria, caused by *Plasmodium falciparum*, remains the most prominent, triggering severe anaemia and pregnancy complications.
Intestinal helminthiases are also widespread, particularly among pregnant women and young children. Hookworm infection (*Ancylostoma duodenale* and *Necator americanus*) leads to chronic blood loss from the intestinal mucosa, worsening iron-deficiency anaemia. Other common presentations include trichuriasis and ascariasis, often linked to inadequate sanitation and safe water access.
Accurate identification of parasites guides appropriate treatment regimens and prevents drug resistance caused by presumptive prescribing. Laboratory personnel use several modalities depending on the suspected organism.
Parasitic infections during pregnancy create dangerous physiological stresses. Malaria in pregnancy sequesters in the placenta, impeding nutrient exchange and leading to low birth weight, maternal anaemia, and congenital transmission risks.
Midwives play a frontline role in mitigation. Intermittent Preventive Treatment in pregnancy (IPTp) using sulfadoxine-pyrimethamine helps clear asymptomatic malaria parasitaemia. Routine deworming with safe anthelmintics during the second and third trimesters addresses hookworm-induced anaemia. Health education on insecticide-treated bed nets, clean water, and proper hygiene remains an essential pillar of antenatal care.