NTD Life Cycles and Transmission
Expert-defined terms from the Global Certificate in Neglected Tropical Diseases Management course at LearnUNI. Free to read, free to share, paired with a globally recognised certification pathway.
Autochthonous transmission #
the spread of a disease within a specific geographic area, where the disease is present in the local population and is being transmitted between individuals.
Biomphalaria #
a genus of freshwater snails that serve as intermediate hosts for the parasitic worm that causes schistosomiasis.
Blood #
feeding vectors: insects or other animals that feed on blood and can transmit diseases in the process.
Cercaria #
the free-swimming larval stage of certain trematode flatworms, including the parasites that cause schistosomiasis.
Chronic infection #
a long-lasting infection that can persist for months or even years, often without causing noticeable symptoms.
Dracunculus medinensis #
the parasitic worm that causes Guinea worm disease.
Epidemiology #
the study of how often and where diseases occur in a population, and the factors that influence their distribution.
Fecal #
oral transmission: the spread of a disease through the ingestion of contaminated fecal matter, often through contaminated food or water.
Intermediate host #
an organism that is infected by a parasite and serves as a host for the parasite's development, but is not the primary host in which the parasite reproduces.
Loiasis #
a tropical parasitic disease caused by the threadworm Loa loa.
Lymphatic filariasis #
a tropical parasitic disease caused by threadlike filarial worms.
Neglected tropical diseases (NTDs) #
a group of infectious diseases that primarily affect people living in poverty in developing countries.
Onchocerca volvulus #
the parasitic worm that causes onchocerciasis (river blindness).
Opisthorchis viverrini #
a species of liver fluke that is a major cause of cholangiocarcinoma (bile duct cancer) in Southeast Asia.
Parasite #
an organism that lives on or inside another organism (the host) and derives its nutrients from the host.
Reservoir host #
an animal or human that carries and can transmit a parasite or other infectious agent, but does not show symptoms of the disease.
Schistosoma #
a genus of trematode flatworms that cause schistosomiasis, a parasitic disease also known as snail fever.
Snail fever #
see schistosomiasis.
Soil #
transmitted helminths: a group of intestinal worms that are transmitted through contaminated soil.
Transmission #
the spread of a disease from one host to another.
Trypanosoma brucei gambiense #
the parasite that causes African sleeping sickness in West and Central Africa.
Trypanosoma brucei rhodesiense #
the parasite that causes African sleeping sickness in East and Southern Africa.
Vector #
an organism (such as a mosquito or fly) that transmits a disease from one host to another.
Wuchereria bancrofti #
the parasitic worm that causes lymphatic filariasis, also known as elephantiasis.
Autochthonous transmission #
Autochthonous transmission refers to the spread of a disease within a specific geographic area, where the disease is present in the local population and is being transmitted between individuals. This is in contrast to imported cases, which are cases of the disease that are brought into the area by individuals who have acquired the disease elsewhere. Autochthonous transmission is an important concept in the epidemiology of neglected tropical diseases (NTDs), as it indicates that the disease is being transmitted within the local community and is not simply the result of imported cases.
Biomphalaria #
Biomphalaria is a genus of freshwater snails that serve as intermediate hosts for the parasitic worm that causes schistosomiasis. Schistosomiasis, also known as snail fever, is a parasitic disease that is transmitted to humans through contact with contaminated water. The parasitic worm that causes the disease, Schistosoma, infects certain species of freshwater snails, including those in the genus Biomphalaria. The snails release the parasite's larvae, called cercariae, into the water, where they can infect humans who come into contact with the contaminated water.
Blood #
feeding vectors: Blood-feeding vectors are insects or other animals that feed on blood and can transmit diseases in the process. These vectors can include mosquitoes, ticks, fleas, and other bloodsucking insects. Some NTDs, such as African sleeping sickness and lymphatic filariasis, are transmitted through the bite of an infected vector. These vectors can carry the parasites or other infectious agents that cause NTDs in their saliva, and can transmit the disease to humans when they bite.
Cercaria #
A cercaria is the free-swimming larval stage of certain trematode flatworms, including the parasites that cause schistosomiasis. Cercariae are released into the water by infected freshwater snails, which serve as intermediate hosts for the parasites. Humans can become infected with schistosomiasis if they come into contact with water contaminated with cercariae. The cercariae can penetrate the skin and enter the human body, where they develop into adult worms that can live in the blood vessels of the liver, intestines, or other organs.
Chronic infection #
A chronic infection is a long-lasting infection that can persist for months or even years, often without causing noticeable symptoms. Chronic infections can occur when the body is unable to completely eliminate the infectious agent, or when the infectious agent is able to evade the immune system. Some NTDs, such as schistosomiasis and lymphatic filariasis, can cause chronic infections that can lead to serious health problems if left untreated.
Dracunculus medinensis #
Dracunculus medinensis is the parasitic worm that causes Guinea worm disease. Guinea worm disease is a parasitic infection that is transmitted through the ingestion of contaminated water. The parasite develops in the body for about a year before emerging through the skin, causing a painful, blistering rash. Guinea worm disease is a painful and debilitating condition that can lead to secondary infections and other complications. It is a neglected tropical disease (NTD) that is targeted for elimination by the World Health Organization (WHO).
Epidemiology #
Epidemiology is the study of how often and where diseases occur in a population, and the factors that influence their distribution. Epidemiologists use a variety of methods to study the spread and impact of diseases, including surveillance, data analysis, and laboratory testing. The study of epidemiology is important for understanding the causes and consequences of diseases, and for developing effective strategies for preventing and controlling their spread.
Fecal #
oral transmission: Fecal-oral transmission is the spread of a disease through the ingestion of contaminated fecal matter, often through contaminated food or water. This type of transmission is common for a number of NTDs, including trachoma, soil-transmitted helminths, and schistosomiasis. Fecal-oral transmission can occur when people come into contact with contaminated water or food, or when they engage in poor hygiene practices, such as not washing their hands after using the toilet.
Intermediate host #
An intermediate host is an organism that is infected by a parasite and serves