Introduction and classification and cost of parasites Flashcards
What is the definition of parasitism?
A non-mutual relationship between species, where the parasite benefits at the expense of the host
What are some general “rules” of parasitology (which may be broken?)
- Parasitism - a non-mutual relationship between species, where the parasite, benefits at the expense of the host.
- Both parasites and hosts have evolved with each other and adapted to each other
- Parasites don’t aim to kill their host
- Parasites can be facultative or obligate
Give an example of an animal which showed parasitism when forced to by circumstance?
Tell me about this parasite and the symptoms it can cause in humans?
The Rat-tailed maggot
- these are the larvae of certain specied of hoverflies
- They live in stagnancy, oxygen-deprived water, with a high organic content
- there have been documented cases of human intestinal myiasis caused by these aggors
- the symmtoms of this are: can be asymptomatic or abdominal pain, nausea, vomiting and pruritus ani
- infection can be caused by ingestion of contaminated food or water
Give some examples of parasites which can live on other parasites
- Nosema podocotyloidis n. sp. (Microsporidia), a hyperparasite
- Parapristipoma octolineatum- a host
- Podocotyloides magnatestis- (Trematode) a parasite
The life cycle of Dipylidium caninum
What are the ways in which diseases can be caused by parasites?
provide an example
- Parasites do direct damage (Dermatobia hominis- human bott fly
Physical and Chemical damage)
- Damage through hyper-immune responses
Culicidae
Aedes aegypti
- Most diseases is because the parasite acts as a vector for other pathogens (Encephalitis viruses)
Some parasitic insects spread diseases. The mosquito is an example of a parasite which spreads viruses
Give an example of a disease which can occur due to the viruses in which mosquitos carry
Some parasitic insects spread diseases
Mosquites VIRUSES
Arboviruses - ARthropod-BOrne virus
Encephalitis viruses is caused by arbovirus which is a disease caused by an arthropod e.g., mosquito
Give some examples of mosquito-transmitted viral diseases causing encephalitis
- Eastern equine encephalitis
- Japanese encephalitis
- La Crosse encephalitis
- St. Louis encephalitis
- West Nile virus
- Western equine encephalitis
- Dengue Fever
- Rift Valley Fever
- Yellow Fever
Give some other examples of mosquito-borne diseases
- Chikungunya virus
- Zika virus
Give examples of other mosquito pathogens
Plasmodium falciparum and others – Malaria
Wuchereria ssp- elephantiasis
Is most parasitic damage direct or indirect?
Give an example
Much (most) parasitic damage is indirect- biting midge- (Culicoides)
WHO- priotory infectious diseases 45% parasitic diseases or related to parasites
Diseases by protozoa and helminths
Tell me where the economic cost of parasitic diseases arises
Nearly half of the world’s population is at risk of malaria.
In 2015,
- ~212 million malaria cases
- ~429 000 malaria deaths (80% under 5 years of age)
Economic costs- Malarial costs – 1% of GDP of all countries were endemic
Direct - (illness, treatment, premature death) at least US$ 14 billion per year.
Indirect -The cost in lost economic growth is ~5 times more than that (estimated at 5% GDP).
700 million people are infected with known mosquito transmitted disease
Context
- 36.7 million people globally were living with HIV (end 2015)
- 2.1 million people became newly infected with HIV (end 2015)
- 1.1 million people died from AIDS-related illnesses (end 2015)
Direct costs (illness, treatment, premature death) at least US$ 19 billion per year
Where does the word parasite come from?
First used in English in 1539, the word parasite comes from the Medieval French parasite, from the Latin parasitus, the latinisation of the Greek παράσιτος (parasitos), “one who eats at the table of another” and that from παρά (para), “beside, by” + σῖτος (sitos), “wheat”, hence “food”. (Wikipedia).
What is a parasite?
There may be more than one definition
- An animal or plant that lives in or on another animal or plant and gets food or protection from it.
- A parasite is a small animal or plant that lives on or inside a larger animal or plant and gets its food from it.
- An animal or plant that lives in or on another (the host) from which it obtains nourishment. The host does not benefit from the association and is often harmed by it.
- An organism that lives on or in a host organism and gets its food from or at the expense of its host.
- An animal or plant that lives on or in another animal or plant of a different type and feeds from it.
What is parasitology?
- The branch of biology or medicine concerned with the study of parasitic organisms.
- A branch of biology dealing with parasites and parasitism especially among animals.
- The branch of biology dealing with parasites and the effects of parasitism.
- A scientific study of parasites, their hosts, and the relationship between the parasite and the host.
- The branch of microbiology that is concerned with the study of parasites. In the process, it gives focus to various characteristics of the parasite (morphology, life cycle, ecology, taxonomy, etc), the type of host they infect/affect and the relationship between the two.
- The study of the interaction between parasites and their hosts. In general, parasitologists tend to concentrate on eukaryotic parasites, such as lice, mites, protozoa, and worms, with prokaryotic parasites and other infectious agents the focus of fields such as bacteriology, microbiology and virology.
- The study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question but by their way of life.
Why should we study parasites?
- They have fascinating, complex and often bizarre life cycles
- They are everywhere
- They have huge medical, sociological, and economic impacts
- They are the reason sex evolved
- They have amazing morphological, immunological, biochemical, molecular, and behavioural adaptations (and may change the behaviour of their hosts).
- We have a morbid fascination with the macabre.
What was the earliest known parasite?
How were they arranged and what effect did they have on their host?
Tube casts on shells of brachiopods from early Cambrian 512 MYA
Orientate with siphonophores, whether single or multiple tubes
Estimated biomass of shells with tubes sig lower than shells without
Estimated biomass of shells increases with distance of tubes from shell opening
Examples of earliest known human parasites? Archaeology
Coprolites:
~6100-7100 BC – Whipworm Eggs - Turkey
~5900 BC - lung fluke eggs – Chile
~5000 BC hookworm eggs – Brazil
~2330 BC – roundworm eggs – Peru
Mummified:
~3000 BC – tapeworm eggs - Chile
~2300 BC – tapeworm eggs – NW Iran
~2000 BC - tapeworm eggs – Egypt
Ancient Egypt – calcified Dracunculus worm – “Mummy 1770”
~1100 BC – filarial worm – Natsef-Amun mummy
~2000 BC – Trypanosoma DNA - Chile
~ 400 BC – Tollund Man – Trichuris, Taenia, Ascaris eggs and proteins
Pelvic Soil:
~8300-7300 BC – roundworm, whipworm, Taenia, Fasciola – Cyprus
~7000-5700 BC – roundworm, whipworm, tapeworm? China
~4000-5800 BC – schistosome eggs – N. Syria
What was the earliest known parasite awareness? History
Egyptian medical papyri
Ebers Papyrus (c1550 BC) guinea Worm - “Wrap the emerging end of the worm around a stick and slowly pull it out.“ (this is where the WHO logo originated from)
Kahun papyrus c1800 BC (and numerous others) – the ‘ā – a – ā disease’ – haematuria - schistosomiasis
China – 3000–300 BC - roundworms, tapeworms, blood flukes, intestinal flukes, hookworms, and head lice
India – 2500-200 BC
Greece – 800-300 BC
Rome - 700-400 BC – Cethegus (160 BC – attempt to drain the Pontine Marshes)
What was the earliest reference to parasites?
Mentuhotep II c2051–2000 BC
Elephantiasis?
Whats symbiosis?
Any relationship between 2 dissimilar organisms
Includes parasitic, commensalistic, and mutualistic relationships between different species (both harmful and beneficial)
Whats mutualism?
Give an example of an organism that shows this
Where two organisms of different species exist in a relationship in which each individual benefits from the activity of the other
Obligate (essential) vs facultative (optional)
Often referred to as symbiosis in the UK!
e.g., lichen which is an association between a fungus and an alga where both benefit from the association - is obligate for the fungus, not necessarily for the alga
Whats commensalism?
In what different ways is this done?
A relationship between two organisms of different species, where one organism benefits from the other without affecting it.
com- (with) and mensa (table)
- food
- shelter (inquilinism)
- transport (phoresy)
- use something created (metabiosis)
Whats a saprophyte/ saprotroph?
An organism that derives benefit (nutrition) from dead or decaying organic matter
Dead or decaying plant matter (saprophyte)
Dead or decaying carrion (saprotroph)
Whats meant by parasitism?
A non-mutual symbiotic relationship between species, where one species, the parasite, benefits at the expense of the other, the host.
Unlike predators, parasites typically do not kill their host, are generally much smaller than their host and will often live in or on their host for an extended period.
The term is generally reserved for eukaryotic organisms, so viruses and bacteria are not normally included
Parasite zoonotic diseases endemic in the UK
Parasite zoonotic diseases exotic to the UK
Parasites are the reason for sex
explain the red queen hypothesis- Host-parasite-evolutionary dynamics
In Lewis Carroll’s “Through the Looking Glass and what Alice found there” the red Queen notes that “it takes all the running you can do to keep in the same place”
Hosts are under huge selection pressure to evolve to evade / counter parasites
Parasites are under huge selection pressure to circumvent host
A continual “arms race” of adaptation & counteradaptation (running to keep in the same place).
The Red Queen argues that host-parasite coevolution favours sexual individuals because they produce offspring with a variety of rare genotypes. In contrast, parasites rapidly adapt to infect common asexual lineages and drive them down in frequency
Selective sweeps and negative frequency-dependent selection
