definitive host

Examples of definitive host in the following topics:

• Hydatid Disease

  • The parasite responsible for polycystic echinococcosis, Echinococcus vogeli, uses dogs or bush dogs as a definitive host and rodents as an intermediate hosts.
  • Echinococcus granulosus is a tapeworm found in dogs, who function as the definitive host, as well as sheep, cattle, goats, and pigs who serve as intermediate hosts.
  • The adult Echinococcus granulosus targets the small bowel of the definitive hosts and release eggs through the feces.
  • The definitive host will then become infected upon ingestion of the cyst-containing organs of the infected intermediate host.
  • It is within the definitive host that the cyst will develop into the adult stage and the cycle continues and repeats .

• Toxoplasmosis

  • Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii and its life cycle mandates a definitive host which are cats.
  • Toxoplasmosis is found in humans worldwide, but the definitive hosts are cats.
  • The known definitive hosts for Toxoplasma gondii are members of family Felidae (domestic cats and their relatives).
  • The intermediate hosts in nature (including birds and rodents) become infected after ingesting contaminated soil, water, or plant material.
  • Cats, can become infected after consuming intermediate hosts that are infected with tissue cysts or by ingesting sporulated oocysts .

• Tapeworms

  • The mammal host is considered the definitive host as this is the site of worm reproduction.
  • The immature eggs are passed through the feces of the mammal host and then infect a freshwater host.
  • This freshwater host is considered to be the intermediate host.
  • The intermediate host is then ingested by a second intermediate host which includes the fish.
  • The larvae develop into a more mature form and constitute the infective stage for the definitive host.

• Babesiosis

  • Babesiosis is a malaria-like parasitic disease caused by infection with Babesia, a parasite transmitted to human hosts by ticks.
  • The Babesia microti life cycle includes two hosts, a rodent, primarily the white-footed mouse, and a tick.
  • During a blood meal, the tick introduces sporozoites into the mouse host.
  • The definitive host, the tick, will then ingest both types of gametes (upon another blood meal).

• Extent of Host Involvement

  • Host-pathogen interactions are the interactions taking place between a pathogen (e.g. virus, bacteria) and their host (e.g. humans, plants).
  • Host-pathogen interactions are the interactions that take place between a pathogen (e.g. virus, bacteria) and their host (e.g. humans, plants).
  • By definition, all pathogens damage their host to some extent.
  • The appearance and severity of disease resulting from the presence of any pathogen depends upon the ability of that pathogen to damage the host as well as the ability of the host to resist the pathogen.
  • Primary pathogens may also cause more severe disease in a host with depressed resistance than would normally occur in an immunosufficient host.

• Ecology, Epidemiology, and Evolution of Pathogens

  • Pathogens have evolved to adapt to their environment and their host in order to survive.
  • Diseases transferred from nonhuman to human hosts are known as zoonoses.
  • Under disease invasion, when a parasite invades a new host species, it may become pathogenic in the new host.
  • One definition of this is the host's parasite-induced loss of fitness.
  • This might induce faster host death, and act against the parasite's fitness by reducing probability to encounter another host (killing the host too fast to allow for transmission).

• Symbiosis

  • Most scientists accept this definition, but some restrict the term to only those species that are mutualistic, where both individuals benefit from the interaction.
  • The host is usually weakened by the parasite as it siphons resources the host would normally use to maintain itself.
  • The parasite, however, is unlikely to kill the host.
  • This is because the parasite needs the host to complete its reproductive cycle by spreading to another host.
  • The eggs of the tapeworm are ingested by the host.

• Protozoa

  • While there is no exact definition for the term protozoa, it often refers to a unicellular heterotrophic protist, such as the amoebas and ciliates.
  • The life stages of these protozoa play a major role in their ability to function as pathogens and infect various hosts.
  • Being a cyst enables parasitic species to survive outside of a host, and allows their transmission from one host to another.
  • The life cycle of protozoan are successful based on successful transmission between hosts and host and environment.

• Phage Display

  • A phage or bacteriophage is a virus capable of infecting a bacterial cell, and may cause lysis to its host cell.
  • When the strain is virulent, all the synthesis of the host's DNA, RNA and proteins ceases.
  • The phage genome is then used to direct the synthesis of phage nucleic acids and proteins using the host's transcriptional and translational apparatus.
  • The new phages produce lysozyme that ruptures the cell wall of the host, leading to the release of the new phages, each ready to invade other bacterial cells.

• Host Range

  • A virus' host range is the range of cell types and host species a virus is able to infect.
  • Non-specific host defenses function early in an encounter with a virus to prevent or limit infection, while the specific host defenses function after infection in recovery to provide immunity for subsequent challenges.
  • The host has many barriers against infection that are inherent in the organism.
  • If a host lacks the receptor for a virus, or if the host cell lacks some component necessary for the replication of a virus, the host will inherently be resistant to that virus.
  • structure of ICAM-1 molecule that enables viruses to bind to host's cell membrane.