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Flashcards in Cardiovascular - Parasites of the CVS Deck (17)
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What is Babesia divergens, and where can it be seen in a blood smear?

Babesia divergens is a protozoa that causes Babesiosis  cattle. In a blood smear, it can be seen as small, dark, pink splotches lying to the periphery within RBCs.


What is babesiosis in cattle, and how is it transmitted?

Babesiosis in cattle is a pathogenic protozoal disease caused by infection by Ixodes ricinus tick.

It leads to haemolytic anemia, haemoglobinuria (haemoglobin in urine ), fever

- Babesia divergens (pathogenic species that affects oxen) multiplies in RBCs by budding to form daughter cells 
- Daughter cells disrupt RBC & are released to infect new RBCs
- Antigen is also released, adsorbed onto other RBCs



What is the pathogenic babesia species that infects dogs, and what is the vector?

Babesia canis is pathogenic babesia that infects dogs

Dermacentor & brown dog ticks infect European dogs; also transovarial transmission


What are four major parasites that infect the cardiovascular system of veterinary species?

Hint: split up into cardio & vascular parasites


Dirofilaria (Heartworm)

Angiostrongylus vasorum (Lungworm)


Blood cells:

Babesia (esp. B. divergens, B. caninum) - attack RBCs

Leishmania - attack macrophages



What are dirofilaria?

Which species of dirofilaria is pathogenic? Why?


Dirofilaria is a nematode (round worm). 

Dirofilaria immitis is the pathogenic species, but it is the female D. immitis worm that causes damage through her production of microfilariae (L1; early-stage worms), not eggs, into peripheral circulation, where they can live for up to two years.

D. immitis female can grow up to a foot long, and males half a foot long. They can live up to seven years and up to 250 can live in the heart & pulmonary artery.

 They trigger diffuse eosinophilic reaction in lung parenchyma; can cause multisystem dysfunction


Which veterinary species are susceptible to Dirofilaria immitis in the UK?

How is it transmitted?

Mostly dogs are susceptible; cats & ferrets less so. 

It is transmitted in the UK by mosquito bite.

The mosquito takes up circulating microfilaria (L1) when it  takes a blood meal from a host. 

The microfilaria moults to L3 in the mosquito.

The mosquito takes another blood meal, and deposits the L3 into the skin, the larva moults to L4.

The L4 moults to L5, a young adult, and penetrates a large vein, ending up in the heart and eventually the .pulmonary arteries. Then they migrate back to the right ventricle.

From there, females release microfilaria into the circulation. 


How long does it take for the new Dirofilaria immitis females to produce microfilaria that enter the circulation after infection?

Six to seven months post-infection.


What are the similarities between Dirofilaria immitis & Astrongylus vasorum

Both are nematode parasites that infect dogs.

As adults, they both reside in the pulmonary arteries and the right side of the heart.

Both use intermediate hosts as vectors.


What are the differences between D. immitis & A. vasorum?

Unlike D. immitis, A. vasorum are very small, with adults reaching only about two cm long (vs. D. immitis, the females of which can grow up to a foot long)

Unlike D. immitis, A. vasorum is widespread in the UK.

Unlike D. immitis, A. vasorum infects both dogs & foxes but doesn't infect cats & ferrets. Foxes might be reservoirs of infection.

Unlike D. immitisA. vasorum uses a slug as its intermediate host, not a mosquito.

Unlike D. immitis, A. vasorum's L1 migrates from alveoli up into trachea, where it's swallowed & excreted in faeces, where it is taken up by the intermediate host, the slug (D. immitis' intermediate host, the mosquito, takes up microfilaria directly during blood meal)

Unlike D. immitis, A. vasorum's intermediate host, the slug, transmits the L3 stage of the parasite when it is eaten by the final host, the dog or fox (Mosquito drops off L3 in skin of dog after a bite).

Unlike D. immitis, A. vasorum migrates from GIT after having been eaten via mesenteric lymph nodes up into the blood stream to the heart. (D. immitis enters bloodstream directly from skin after puncture by mosquito)

Unlike D. immitis, A. vasorum takes about seven weeks to release eggs into pulmonary capillaries. (D. immitis took up to seven months, and released them into the circulation)


How does Leishmania differ from Babesia in terms of epidemiology? 

Leishmania is transmitted via sandflies (Phlegbotomus spp & Lutzomyia) mainly in southern Europe, Africa and Asia. 

Babesia is spread by ticks (Ixodus rhinus & Dermocenter) that do exist in the Western UK especially. 



What types of animals are most susceptible to Leismania?

Dogs, cats, humans, wild animals (foxes, rodents).


Leishmania is a protozoan, intracellular parasite that uses an intermediate host. What is the life cycle? 

Two main stages: promastigote & amastigote.

The amastigote stage mature in macrophages.

Dog is bitten by sandfly & infected with promastigotes.

Promastigotes enter circulation & invade macrophages.

Macrophages die, releasing amastigotes, which infect more macrophages 


Macrophages ingested by sandfly taking blood meal

Amastigotes released into sandfly gut, they mate and produce promastigotes


Would a cow on her third calf be susceptible to contracting babesiosis? 

Yes. Calves YOUNGER than nine months tend to be refractory.


What are the two known forms of Leishmaniasis?

Cutaneous, affecting skin, and Visceral, affecting internal organs.


Both Leishmania & Babesia are protozoa parasites transimitted via intermediate hosts to their final hosts. How do the life cycles differ

Leishmania is transmitted to dogs, humans and other  animals such as horses, cats and foxes by sandflies, which are prevalent in warmer climates of Southern Europe, for example. 

The early stage of the protozoa, the promastigote, is injected into the animal via a sandfly bite. The promastigote enters the circulation and macrophages, where it matures, differentiates and reproduces amastigotes. These either break out of the macrophages go invade other macrophages in the blood, or they are taken up by sandflies taking a blood meal. Inside the sandfly gut, the amastigotes reproduce promastigotes. 

Babesia is transmitted mainly to oxen and dogs via ticks that are common in the UK -- the Ixodus rhinus transmits the protozoa to cattle & the Dermacentor or brown tick transmit it to dogs. 

Once the tick takes a blood meal from the oxen or dog, the infectious sporozoite enters from the tick's saliva.  The sporozoites invade RBCs and bud into merozoite daughter cells (2-4 daughter cells). Some will produce gametocytes. Another tick comes to take a blood meal, ingesting the infested RBCs. Inside the tick gut, the gametocytes form zygote, and then invade salivary gland, hatch out as sporozoites.


How can oxen be protected against Babesia?

There's no UK vaccine, so the best protection is chemical treatment against ticks:


Not there are strict withdrawal periods: 7 months for meat, 3 weeks for milk)


How can dogs be protected from Babesia?

Anti-tick treatment such as fipronil spot-on treatment or amitraz collar.

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