Protozoa problem-solving session

What can be seen within the red blood corpuscles?

abnormal inclusions

This blood smear was taken from a replacement dairy heifer that was bought onto a farm with lots of rough grazing. Signs included anaemia, haemoglobinuria, fever and lethargy.

Identify the parasite.

babesia divergens

Why did this animal succumb to babesia divergens and not others that were reared on the same farm?

• it did not have immunity

• animals on the farm were likely to have immunity as a result of exposure to infection early in life while partially protected by maternal antibodies

What cows are at higher risk of disease from babesia divergens?

immunologically naiive hosts brought into endemic areas

A client who raises laying hens on straw bedding sends you this photograph of the caeca of a bird that was found dead.

Which parasite is likely to have caused this?

coccidiosis (in particular a species of EImeria that infects the caeca, such as E. tenella)

Name 2 factors that straw bedding provides, which are conducive to infection with this parasite

• intact faeco-oral cycle

• high moisture and temperature suitable for development to the infective stage

Structures observed under high power magnification of a preparation in the faeces of a rabbit showing lethargy, dehydration and diarrhoea.

Name the parasite

Eimeria sp. or coccidiosis

What does Eimeria stiedae cause in rabbits?

hepatic coccidiosis

What causes hepatic coccidiosis in rabbits?

Eimeria stiedae

Is it easy to distinguish different species of Eimeria?

NO

Name the life cycle stage

oocyst

How long can the oocyst (as shown in the image) survive in the environment in optimal conditions (1 week/1 month/1 year)?

a year or more

What is survival of an oocyst reduced by?

• desiccation

• high temperature

• e.g. in compost or by disinfection

What kind of animal is this?

tick

Name protozoal diseases that ticks carry

• babesia canis

• babesia divergens

What does this image show?

life cycle of the coccidian parasite (Eimeria sp.)

Name the lifecycle stage labelled 1

schizogony or merogony

Name the lifecycle stage labelled 2

gametogony

Name the life cycle stage labelled 3

sporulation

A blood smear from a cow in Tanzania that is weak, emaciated, and no longer gives milk.

Name the parasite

Trypanosoma brucei

A blood smear from a cow in Tanzania that is weak, emaciated, and no longer gives milk.

What sickness does Trypanosoma brucei cause in humans?

sleeping sickness, or human African trypanosomiasis (HAT)

A photomicrograph of a cystic structure found during histological examination of a mouse’s brain, as part of a research project investigating parasite-induced modification of animal behaviour.

Name the parasite

toxoplasma gondii

What are the consequences of infection with toxoplasma gondii in an adult cat?

• none or minimal

• possible some transient diarrhoea

• kittens can be infected in utero and be born weak

What are the consequences of infection with Toxoplasma gondii in a pregnant sheep?

• abortion

• stillbirth

• apparently barren

What are the consequences of infection with toxoplasma gondii on a pregnant human?

• possible miscarriage

• a child infected in utero can develop retinal lesions and vision loss

What are the consequences of infection with toxoplasma gondii in a healthy, non-pregnant, immunocompetent person?

• none or minimal

• flu-like sings

• bradyzoite cysts can establish in the brain but are unlikely to lead to clinical disease, though could affect behaviour

What are the consequences of infection with Toxoplasma gondii in a person suffering from AIDS?

generalised, tachyzoite infection that can be fatal

A photomicrograph of a protozoal parasite associated with diarrhoea in dogs. Name the parasite

Giardia

Can Giardia be zoonotic?

• in principle YES

• in practice, most strains seem to circulate separately in dogs & humans

• probably more human-to-dog than dog-to-human transmission

A blood smear from a dog returning to the UK after a summer holiday in the south of France, having collapsed 2 weeks later with acute anaemia.

What is the parasite?

Babesia canis

What protozoal parasite is transmitted by this insect?

Leishmania

What is this insect?

sandfly