8.1 Parasite Diversity Flashcards
Parasite diversity
Parasites are found in multiple taxonomic groups
Virus
Bacteria
Fungus
Protists
Nematodes
Platyhelminths
Arthropods
Virus
How diverse are viruses?
How many viral types are found in 200L of seawater?
What do viruses use?
Estimated number of viruses: 10^31 i.e 30 zeros
Most common are called phages and infect bacteria
~5000 viral genotypes in 200L of seawater, most of which are phage viruses
ALL viruses are obligate parasites
ALL use the host machinery
Various viruses infecting a large array of hosts
Different mode of replications
Example of viruses
Chicken pox (varicella zoster)
Myxomatosis (Myxoma virus) - rabits
Ebola virus - Influenza virus
Almost all taxon have viruses. There are also viruses of viruses (hyperparasitism)
Viruses cause a large number of important diseases in human
Some viruses are being used as pest control agents (Rabbit Australia)
Bacteria
How much bacteria make up human?
What is the relationship between most bacteria and host humans?
Gut is expected to carry more bacteria than cells
Most bacteria are commensals or mutualists
(change in number/composition can affect regulation pathway , e.g. Crohn’s disease)
Many are parasitic of humans and of plants and animals.
Such as leprosy, TB
Bacteria
Very large phylogeny
Gram-negative – mix, not thick
Gram-positive – thick layer of peptidoglycan
Examples:
Fungus
Examples?
Usually not threatening to human health (e.g. ringworm)
- Cordyceps sp*. on african ant
- Puccinia graminis* black stem rust of wheat
Fungus
Cordyceps sp.
Cordyceps is a species complex with over 400 species
Parasites of insects and arthropods
Species are specialists parasites with one or a low number of hosts
Found mainly in subtropical and tropical regions
Protozoa
- *Definition**: ‘Protozoa’ used to refer to a single phylum of eukaryotic single-celled organisms, but with the advent of electron microscopy and molecular systematics this single phylum has been split into around ten phyla, and the word ‘protozoa’ is now usually used as a colloquialism to describe this group, which is often grouped into a kingdom, the ‘protista’
- *Include some of the most important diseases in humans and animals**
Protist: Nosema apis
& Nosema ceranae
Microsporidia parasites (small single cell eukaryotes)
Obligate parasites. Infect midgut epithelium and will kill the infected bees.
Infected queen => entire colony dies.
Flabelliforma magnivora
How is it transmitted?
Dapnia how can they reproduce?
Almost 100% vertically transmitted
Daphnia have two modes of reproduction
- Sexual
- Asexual way – pathenogensis in which the parasite will be passed onto the offspring
Infect ovaries and can drive population of Daphnia to extinction
Can have drastic consequences for ecosystems since daphnia are often feed for fish larvae and small fish
Giardia lamblia
How does it multiply?
Multiplies by binary fission
Flagellated protozoan
Reproduces in small intestine
Causes chronic diarrhea
Although many infected people show little evidence of disease, in others the pathology can be severe, with symptoms similar to dysentery, often accompanied by intestinal pain
Zoonotic species = can be transmitted from animals to human
324 confirmed cases in Reno, Nevada
Water contamination linked to beaver
Beavers are reservoir of the parasite
Bird Malaria
It has the same life cycle as the human malaria, parasite will infect mosquito which will feed on a bird and the parasite will spread
Multiple ideas what happens when birds invade ecosystsm
- If you invade a new system you are escaping from native parasite and you should be resistant to everything you find
- by looking at sapprow - they were more infected by the native
Nematoda
Are they all parasites
What can they inhabit
What is the symmetry?
Do they have a circulatory or respiratory system?
What muscles do they have?
Diverse & Abundant
e.g roundworms
NOT ALL PARASITES
Free living in soils
Feed on detritus and bacteria for instance
Bilaterally symmetrical
Well developed digestive, reproductive and nervous systems
No circulatory or respiratory system
Accomplished by movement of fluids in body
Longitudinal muscles, but no circular muscles
Size range: 0.003in. To 27 feet! (giant sperm whale nematode)
Example 1 Nematoda: Trichuris
Trichuris trichuria (whipworm) embedded in the intestinal mucosa.
How many people thought to be infected?
How are eggs passed?
~1 billion people infected
Most cases are asymptomatic
Eggs are passed with host’s stool
Eggs become infective in 15 to 30 days
Example 2 Nematoda: Ascaris lumbricoides
807-1,221 million people worldwide infected (CDC 2011)
Migrate in human body for moulting
Intestine then back to the lungs (matures x2)-trachea-throat-stomach- small intestine (mature)
Nematoda: Wuchereria bancrofti
Wuchereria bancrofti – vector feeding on blood of a human – produce a larvea – long and skinny shape – going to move around in the body – new vector feeding infected with different moulting stages – reach the gut of the vector then come back to the head – allow the vector to feed on the host
Pathology is caused by inflammation and blockage of the lymph ducts.
Most extreme form called elephantiasis..
Nematoda: filarial nematodes
Pathology is caused by inflammation and blockage of the lymph ducts.
Most extreme form called elephantiasis.
Nematoda: filarial nematodes
Helminthiasis filarrid
Causes river blindness
Another case of nematoda – filarial nematodes – this is interesting because often when we think of parasites – slightly different
Vector is a black fly – what happens is that black fly will get infected – form many small larvae
