Yes, they rot.
But, most of them are microscopic, so blood takes care of it.
But sometimes, dying parasites may cause serious health problems.
Heartworm (large worm that rarely infects human) may even cause death.
Most blood and tissue parasites (except few) are microscopic.
Tapeworm larvae (non microscopic) may infect brain.
There are a number of Cestodes(Tapeworms)- that have man as the main definitive host, in addition a number of Cestodes normally infecting animals may cause accidental infections in man. These infections may be either by the adult form of the parasite (i.e. a tapeworm), or more seriously by the larval parasite.
Cestodes (adults and larvae) that may infect human:
- Taenia saginata - Beef Tapeworm
- Taenia solium- Pork Tapeworm. Man may also be infected by larval forms of this parasite (Cysticercosis) (#1 reason why Jews, muslims and members of some other religions don't eat Pork )
- Hymenolepis nana - Dwarf Tapeworm
- Hymenolepis diminuta - Rat Tapeworm
- Dipylidium caninum - Dog tapeworm
- Echinococcus granulosus - Hydatid disease
- Echinococcus multilocularis- Alveolar Hydatid disease
- Taenia solium- Cysticercosis in man, but the larvae are more normally found in the pig. Man may also be infected by adult forms of this parasite (the Pork Tapeworm)
- Spirometra mansonoides- Causes sparganosis in man.
- Spirometra proliferum - Causes a branching sparganosis where the larvae may bud off to form new spargana in the tissues. Has been reported a few times from Japan and the USA. Nothing else is known about this parasite in terms of the lifecycle or adult worms.
- Mesocestoides variabilis - A very rare parasite of man, identified from a child in East Texas and another case in Denmark. Normally parasitic in foxes, skunks, dogs and racoons in the USA.
- Bertiella studeri - a rare parasite of man, normally parasitic in apes and monkeys
- Inermicapsifer arvicanthidis - A common parasite of rodents in Africa, this was first identified in humans in Cuba where it is an uncommon but not rare parasite of man. A few human cases have also been reported from Africa and Mauritius.
- Raillietina siriraji - A rare parasite, identified from children in Bangkok.
- Taenia taeniformis - The adult parasites are normally found in cats, but it has been reported from an Argentinean child.
- Taenia bremneri(Syn. T. confusa) - reported from man in Africa, Japan and USA.
- Echinococcus vogeli - This parasite is found in Central and Northern South America, with bush dogs as the definitive hosts, and pacas and other rodents as the normal definitive host. The cysts resemble E. granulosus, but often become septate , forming multichambered cysts (i.e. polycystic hydatids).
(NB. Not all authors recognise this species, it being very similar to E. granulosus)
- Taenia africanus- reported a few times in East Africa
- Taenia multiceps- The adult Tapeworms of this species are found in dogs and related canids, whilst the larvae, a coenurus, is normally found in the brain or spinal cord of sheep and goats. The larval form may rarely infect man, where it causes coenurus cerebralis, on accidental ingestion of tapeworm eggs in the faeces of dogs.
- Taenia serialis- A similar parasite to T. multiceps, the coenurus larvae usually being found in the subcutaneous and intramuscular tissues of lagomorphs. Has been reported very rarely in man.
- Taenia glomerulatus- The larvae normally infect rodents, but it has also been reported in man in Africa.
- Plasmodium falciparum (malaria) (Also P.vivax, P.malariae, P.ovale - cause less severe forms of malaria).
Malaria - estimated 40% of world's population at risk; 10% severe risk. Major killer of children in tropical Africa. Tropics and subtropics - Africa, Asia and South America. Human is definitive host. Transmitted by mosquitoes - Anopheles
- Trypanosoma brucei rhodesiense and T. b. gambiense:
African sleeping sickness - East African form of disease (Rhodesian sleeping sickness) is acute, West African form (Gambian sleeping sickness) is more chronic. 25,000 cases reported per year, but 55 million estimated at risk. Restricted to tropical Africa, largely rural areas. Transmitted by tsetse fly (Glossina):
- Trypanosoma cruzi: Chagas' disease - initial acute phase of several weeks, subsides into chronic phase, which may continue for decades.
Mega syndromes: Megaoesophagus, megacolon. Heart damage: arrhythmias, dilatation, sudden death. South America; largely disease of poverty - poor housing. 100 million estimated at risk; 16-18 million infected.
- Leishmania donovani, L. tropica, L. mexicana, L. braziliensis:
Visceral and cutaneous leishmaniasis. Widespread in tropics and subtropics. L. donovani causes visceral disease in Old and New Worlds; L. tropica causes cutaneous leishmaniasis (oriental sore) in Old World; L. mexicana and L. braziliensis cause muco-cutaneous leishmaniasis in New World. Transmitted by sandflies - Phlebotomus, Lutzomyia
- Toxoplasma gondii: Toxoplasmosis. Common, but only problematic in AIDS patients or to foetus. Humans are not definitive host - domestic cat and other felines are where full lifecycle including sexual phase takes place.
- Trichomonas vaginalis:
Trichomoniasis - not life threatening, but unpleasantly common infection of vagina in females, urethra in males. venereally transmitted.
- Acanthamoeba castellanii, A. culbertsoni and other species:
Opportunistic infection. Corneal ulcers, common but not life-threatening. Occasional death through invasion of CNS.
- Naegleria fowleri:
Opportunistic infection. Enters via nasal passages from water; invasion of CNS causes fatal meningoencephalitis.