Parasitic diseases
Parasites:
An organism that lives on or in a host organism and Parasitic Helminths
feeds from the host. Live in and feed on a living host
3 major classes that cause disease in humans Cannot reproduce entirely in the host
o Protozoa: Produce eggs that can survive in the
(microscopic,single cell organisms) environment
e.g. Plasmodium Environmental conditions govern egg
o Ectoparasites: hatching
Ticks, fleas, lice, mites “tropical diseases” warm, moist, shaded soil*
Cause disease 2 major classes that affect humans:
Transmitters of disease o Roundworms (Nematoda)
o Helminths: Pinworm, Ascaris,
(large, multicellular organisms) Hookworm, Trichinella,
Include several Filaria, Toxocara (zoonotic)
Neglected Tropical Diseases o Flatworms (platyhelminths)
(NTDs) Liver, intestinal and lung
e.g. Soil-transmitted helminthiasis Flukes; Schistoma; tapeworms
Schistosoma Ascaris
Freshwater intermediate host (snails) Soil-Transmitted Helminth (STH)
Blood fluke (lives in blood vessels, Lives in intestine
liver+messentary mainly) Very large, so can cause things such as
When they are adults, they pair and produce lots blocking the intestines
of eggs Ascaris lumbricoides= most prvelant type
Eggs try to get out of body causing inflammation o Causes Ascariasis
and disease
Common types: Schistosoma mansoni,
No mouse model for Ascaris lumbricoides
japonicumor haematobium
Ascaris suum used in mice and pigs
o Causes Schistosomiasis
Well established mouse models using:
o Schistosoma mansoni Whipworm
o Schistosoma japonicum STH (intestinal)
no full life cycle for haematobium, only the Egg Trichuris trichiura (most common type)
injection that can be modelled in rodents o Causes Trichuriasis
Established models using:
o Trichuris muris (mouse)
Filaria o Trichuris suis (pig)
Intermediate host = Infected mosquitos, blackfly
bite
Wuchereria bancrofti, Brugia malayior
Onchocerca volvulus (most common ones) Hookworm
o WB+BM^ cause Lymphatic filariasis STH (intestinal)
o OV ^ cause river blindness Most common types: Necator americanusor
and Ancylostoma duodenale
Established mouse models using: o Causes Hookworm disease
o Litosomoides sigmodontis
o Brugia malayi Rodent models using:
o Nippostrongylus brasiliensis
o Heligmosomoides polygyrusbaker
, Schistosomiasis (bilharzia) Lymphatic Filariasis
Disease caused by Schistosoma spp. 90% of disease caused by
200,000 deaths a year (WHO, 2014) Wuchereria bancrofti.
0 million suffer severe morbidity* over 120 million infected
Infective cercariae are released into water from freshwater snail (2000)*
intermediate host 40 million disfigured and
Mature into adults in blood vessels incapacitated*
Release eggs which cause pathology in multiple tissue sites Infective L3 larvae enter skin
through a mosquito
Chronic infection and release of eggs can result in chronic intermediate host
inflammation, leading to tissue fibrosis and cancer. Adults live in the lymphatics
Pathologies includes: Release microfilariae which
Hepatosplenomegaly (liver and spleen enlargement) migrate to blood and lymph
Liver fibrosis, liver failure Impairment of the lymphatics
Bladder cancer, colon cancer results in accumulation of
Kidney failure lymph
Genitourinary disease incl. femalegenital schistosomiasis - linked to Swelling is termed
increased rates of HIV transmission “elephantiasis”
Soil-Transmitted Helminths
Ascaris, Whipworm and Hookworm Hookworm
Account for major burden of parasitic disease world wide Pre-clinical model organisms
1.5 billion people (>20%) of the world is infected with a STH include dogs (A. ceylanicum
(WHO, 2020) and A. caninum) and hamsters
Cause 5.2 million disability-adjusted life years (DALYs) (A. ceylanicum and N.
300 million people (20%) suffer from severe morbidity americanus infections).
150,000 deaths annually (patients with heavy infections or who However, both develop natural
are immune-compromised) = 0.01% resistance to infection (unlike
MOST patients are asymptomatic (80%)! human disease).
Common rodent model:
Main species are: Nippostrongylus brasiliensis
o Roundworm (Ascaris lumbricoides) Acute infection – quickly
expelled from mice (9 days)
o Whipworm (Trichuris trichiura)
Causes goblet hyperplasia in
o Hookworms (Necator americanus and Ancylostoma
gut
duodenale) Causes long term lung
Can establish chronic infections in the intestine emphysema and goblet
Cause diarrhoea, abdominal pain, general malaise and hyperplasia
weakness.
May influence cognitive function, learning and development of
children
Ascaris has a lung phase which can cause transient
inflammatory lung disease “Loeffler’s syndrome”
Whipworm can cause intestinal blood loss (anaemia), colitis and
Trichuris dysentery syndrome
Hookworm has a lung phase, which can result in long-term lung
emphysema. Entry into the skin can cause “Ground Itch”.
Intestinal attachment can lead to anaemia and proteinaemia
Parasites:
An organism that lives on or in a host organism and Parasitic Helminths
feeds from the host. Live in and feed on a living host
3 major classes that cause disease in humans Cannot reproduce entirely in the host
o Protozoa: Produce eggs that can survive in the
(microscopic,single cell organisms) environment
e.g. Plasmodium Environmental conditions govern egg
o Ectoparasites: hatching
Ticks, fleas, lice, mites “tropical diseases” warm, moist, shaded soil*
Cause disease 2 major classes that affect humans:
Transmitters of disease o Roundworms (Nematoda)
o Helminths: Pinworm, Ascaris,
(large, multicellular organisms) Hookworm, Trichinella,
Include several Filaria, Toxocara (zoonotic)
Neglected Tropical Diseases o Flatworms (platyhelminths)
(NTDs) Liver, intestinal and lung
e.g. Soil-transmitted helminthiasis Flukes; Schistoma; tapeworms
Schistosoma Ascaris
Freshwater intermediate host (snails) Soil-Transmitted Helminth (STH)
Blood fluke (lives in blood vessels, Lives in intestine
liver+messentary mainly) Very large, so can cause things such as
When they are adults, they pair and produce lots blocking the intestines
of eggs Ascaris lumbricoides= most prvelant type
Eggs try to get out of body causing inflammation o Causes Ascariasis
and disease
Common types: Schistosoma mansoni,
No mouse model for Ascaris lumbricoides
japonicumor haematobium
Ascaris suum used in mice and pigs
o Causes Schistosomiasis
Well established mouse models using:
o Schistosoma mansoni Whipworm
o Schistosoma japonicum STH (intestinal)
no full life cycle for haematobium, only the Egg Trichuris trichiura (most common type)
injection that can be modelled in rodents o Causes Trichuriasis
Established models using:
o Trichuris muris (mouse)
Filaria o Trichuris suis (pig)
Intermediate host = Infected mosquitos, blackfly
bite
Wuchereria bancrofti, Brugia malayior
Onchocerca volvulus (most common ones) Hookworm
o WB+BM^ cause Lymphatic filariasis STH (intestinal)
o OV ^ cause river blindness Most common types: Necator americanusor
and Ancylostoma duodenale
Established mouse models using: o Causes Hookworm disease
o Litosomoides sigmodontis
o Brugia malayi Rodent models using:
o Nippostrongylus brasiliensis
o Heligmosomoides polygyrusbaker
, Schistosomiasis (bilharzia) Lymphatic Filariasis
Disease caused by Schistosoma spp. 90% of disease caused by
200,000 deaths a year (WHO, 2014) Wuchereria bancrofti.
0 million suffer severe morbidity* over 120 million infected
Infective cercariae are released into water from freshwater snail (2000)*
intermediate host 40 million disfigured and
Mature into adults in blood vessels incapacitated*
Release eggs which cause pathology in multiple tissue sites Infective L3 larvae enter skin
through a mosquito
Chronic infection and release of eggs can result in chronic intermediate host
inflammation, leading to tissue fibrosis and cancer. Adults live in the lymphatics
Pathologies includes: Release microfilariae which
Hepatosplenomegaly (liver and spleen enlargement) migrate to blood and lymph
Liver fibrosis, liver failure Impairment of the lymphatics
Bladder cancer, colon cancer results in accumulation of
Kidney failure lymph
Genitourinary disease incl. femalegenital schistosomiasis - linked to Swelling is termed
increased rates of HIV transmission “elephantiasis”
Soil-Transmitted Helminths
Ascaris, Whipworm and Hookworm Hookworm
Account for major burden of parasitic disease world wide Pre-clinical model organisms
1.5 billion people (>20%) of the world is infected with a STH include dogs (A. ceylanicum
(WHO, 2020) and A. caninum) and hamsters
Cause 5.2 million disability-adjusted life years (DALYs) (A. ceylanicum and N.
300 million people (20%) suffer from severe morbidity americanus infections).
150,000 deaths annually (patients with heavy infections or who However, both develop natural
are immune-compromised) = 0.01% resistance to infection (unlike
MOST patients are asymptomatic (80%)! human disease).
Common rodent model:
Main species are: Nippostrongylus brasiliensis
o Roundworm (Ascaris lumbricoides) Acute infection – quickly
expelled from mice (9 days)
o Whipworm (Trichuris trichiura)
Causes goblet hyperplasia in
o Hookworms (Necator americanus and Ancylostoma
gut
duodenale) Causes long term lung
Can establish chronic infections in the intestine emphysema and goblet
Cause diarrhoea, abdominal pain, general malaise and hyperplasia
weakness.
May influence cognitive function, learning and development of
children
Ascaris has a lung phase which can cause transient
inflammatory lung disease “Loeffler’s syndrome”
Whipworm can cause intestinal blood loss (anaemia), colitis and
Trichuris dysentery syndrome
Hookworm has a lung phase, which can result in long-term lung
emphysema. Entry into the skin can cause “Ground Itch”.
Intestinal attachment can lead to anaemia and proteinaemia
