Malaria Biology and Transmission

Malaria

• Caused by the parasite Plasmodium spp., a single-celled protozoan parasite
• Six different species of Plasmodium can infect humans
• Parasites also infect other animals, including primates, rodents, birds, lizards, and amphibians
• People at risk include immunologically naive individuals, predominantly children under 5, and non-immune travelers
• Life cycle involves two hosts: humans and mosquitoes
• Only female mosquitoes transmit the parasite
• Symptoms include acute malaria, fever, chills, anaemia, headache, diarrhoea, and vomiting
• Diagnosis is made through patient history, rapid diagnostic test (RDT), and PCR
• Effective antimalarials are available, but treatment outcomes can be problematic due to resistance, data in pregnancy, and counterfeit drugs

Prevention and Control

• Insect repellent, bed nets, protective clothing, chemoprophylaxis, and mosquito control can prevent malaria
• Two vaccines are available, targeting the sporozoite stage: RTS, S and R21/Matrix M

Cryptosporidium

• Causes cryptosporidiosis (crypto)
• Symptoms include diarrhoea, abdominal pain, nausea, fever, and fatigue
• Transmission occurs through the faecal-oral route, involving ingestion of oocysts in contaminated water
• Life cycle has multiple stages, and the disease is generally self-limiting but can be serious in immunocompromised individuals
• Diagnosis is made through stool sample analysis
• Treatment involves drinking fluids to prevent dehydration, and anti-parasite drugs are available

Prevention and Control

• Good hygiene practices, avoiding contaminated water sources, and boiling or filtering contaminated water can prevent cryptosporidiosis
• No vaccines are currently available

Helminths (Parasitic Worms)

• Term used for all groups of parasitic worms
• Multicellular organisms, including roundworms (nematodes) and flatworms (platyhelminths)
• Roundworms have cylindrical bodies and lack specialized attachment organs
• Flatworms have flat bodies, muscular suckers and/or hooks for attachment, and complex body organization

Helminths Infections

• Infections are common in warmer regions
• Different kinds of parasitic worms infect humans in different ways
• Larval stage: 100-200um, adult worms: cm to m long

Hookworms

• Multiple species of roundworms (nematodes)
• Transmission: eggs hatch into larvae in the soil, penetrate the skin, and are carried to the lung and then to the small intestine
• Symptoms include rash, itch at site of skin infection, mild diarrhoea, anaemia, abdominal pain, and loss of appetite and weight loss
• Diagnosis is made through faecal analysis
• Effective drugs are available, such as albendazole
• Prevention involves avoiding contact with contaminated soil and improving hygiene and sanitation

Prevention and Control

• No vaccines are currently available for hookworms