Protozoa of International Importance

What are protozoa?

• single-celled

• eukaryotes

definitive host

one in which a parasite reaches maturity and usually reproduces sexually

Intermediate host

one in which the parasite develops, but does not reach maturity or reproduce sexually

vector

intermediate host that carries and transmits parasite developmental stages to another host

Name an example of a protozoa that has a direct life cycle

cryptosporidium

Name an example of a protozoa that has an indirect life cycle

toxoplasma

What are the 3 categories of protozoan lifecycles?

• direct

• indirect

• vector-borne

What are the 3 arthropod-borne protozoa of major importance in humans?

• plasmodium (malaria)

• trypanosoma (trypnosomiasis)

• leishmania (leishmaniasis)

What are the arthropod-borne protozoa of major importance in animals?

• trypanosoma

• theileria (theileriosis)

• babesia (babesiosis)

• plasmodium (avian malaria)

• leishmania

What vectors are protozoa/parasites commonly transmitted via?

• fly

• tick

What are the groups of flies that are vectors for protozoa?

• flagellates

• apicomplexa

Which group of ticks are vectors for protozoa?

apicomplexa

Which group of ticks are vectors for bacteria?

rickettsiales

What types of flies are flagellates?

• tsetse flies

• biting flies

• sand flies

What type of flies are apicomplexa?

mosquitoes

What parasites do tsetse flies and biting flies carry?

trypanosoma

What parasite do sand flies carry?

leishmania

What parasite do mosquitoes carry?

plasmodium

What disease does trypanosoma cause?

trypanosomiasis

What disease does Leishmania cause?

leishmaniasis

What disease does plasmodium cause?

malaria

What parasites do apicomplexa ticks carry?

• babesia

• Theileria

What bacteria do rickettsiales carry?

• Ehrlichia

• Anaplasma

What disease does babesia cause?

babesiosis

What disease does Theileria cause?

Theileriosis

What disease does Ehrlichia cause?

ehrlichiosis

What disease does anaplasma cause?

anaplasmosis

What’s the basic tick life-cycle?

1. eggs in engorged female

2. larva

3. nymph

4. adult

What percentage of a ticks life-cycle do they spend on host?

25%

What does this image show?

basic tick life-cycle

What does this image show?

tick egg mass

What does this image show?

tick larva

What does this image show?

tick nymph

What does this image show?

tick adult

What does this image show?

one-host tick lifecycle

Name an example of a one-host tick

rhipicephalus (boophilus) microplus

What is rhipicephalus (boophilus) microplus?

important tropical cattle tick

What does this image show?

two-host tick lifecycle

Name an example of a two-host tick

hyalomma sp.

What is Hyalomma sp.?

important Mediterranean and subtropical livestock tick

What does this image show?

three-host tick lifecycle

Name an example of a three-host tick

ixodes ricinus

What is ixodes ricinus?

familiar UK sheep tick

What are the 2 types of transmission?

• transstadial

• transovarial

What is transstadial transmission?

can only transmit disease in one generation of lifecycle

What is transovarial transmission?

can transmit disease through multiple generations (from parent to offspring)

List 3 important European Tick Species

• Ixodes ricinus

• Rhipicephalus sanguineus

• Dermacentor reticulatus

Which tick species is most prevalent in the UK?

Ixodes ricinus

What cell is babesia a parasite of?

red blood cells

What type of transmission is Babesia transmitted by?

transovarial transmission

What is the main Babesia species in Europe?

Babesia canis

What is Babesia canis transmitted by?

Dermacentor reticulatis

List the 4 canine babesia species that are important in Europe

• babesia (canis) canis

• babesia (canis) vogeli

• babesia gibsoni

• babesia vulpes

Where is babesia (canis) vogeli found?

mediterranean

Where is babesia gibsoni found?

sporadically reported in Europe

Where is Babesia vulpes found?

endemic in northern Spain

What does this image show?

annual incidence of canine babesiosis in Europe

What does this image show?

• 2017 distribution of Rhipicephalus sanguineus

• blue line = previous distribution

What is the pathogenesis of canine babesiosis?

• rapid division of parasite in erythrocytes

• haemolytic anaemia

• splenomegaly

What are the clinical signs of canine babesiosis?

• acute disease

• 1-2 weeks post tick-feeding

• fever

• anaemia

• haemoglobinuria (‘redwater’)

• jaundice

• neurological signs

How do you treat canine babesiosis?

• antiprotozoal drugs

• blood transfusion

How can you diagnose babesia spp.?

• blood smear (Giemsa stain)

• PCR

What does this image show?

babesia spp.

What is shown on the left and right of this image?

• left = babesia divergens

• right = babesia major

What is the size of babesia divergens?

small

What is the size of babesia major?

large

What is the vector of babesia divergens?

ixodes ricinus

What is the vector of babesia major?

haemaphysalis punctata (red sheep tick)

What is the distribution of babesia divergens?

all areas with ixodes ricinus

What is the distribution of babesia major?

S.E. England

Where is babesia divergens important?

in endemic areas

Is babesia major important?

minor importance

What is the vertebrate host of Babesia divergens?

cattle

What is the disease that babesia divergens causes called?

redwater fever

What are the clinical signs of babesia divergens in cattle?

• pyrexia, anorexia, depression

• anaemia, haemoglobinuria, icterus

• diarrhoea or constipation

• occasionally neurological signs

How can you distinguish haemoglobinuria from haematuria?

RBC settle on standing in haematuria

What factors affect the epidemiology of bovine babesiosis in the UK?

• restricted to pastures that support high numbers of ticks

• disease outbreaks associated with peaks of tick feeding activity

• principally a disease of older animals

• inverse age resistance

• enzootic stability develops in endemic areas

What is enzootic stability?

high levels of challenge, but low disease levels

What is inverse age resistance (like seen in bovine babesiosis)?

• calves up to 6 months protected (colostral immunity in endemic areas & innate resistance)

• infected cattle develop non-sterile immunity - immunity prevents further infection

What are the risk factors for outbreaks of bovine babesiosis?

• introduction of babesia naiive adults to tick areas

• introduction of tick-infested cattle to naiive herds

• fluctuations in tick numbers

Why might there be fluctuations in tick numbers?

• land use changes

• changes in pasture harvesting

• presence in dipped sheep

• use of endectocides for helminths

• perturbation of ‘enzootic stability’

What can be put in place to control bovine babesiosis?

• ensure adequate exposure of young animals to ticks before 6 months of age

• treat affected animals

• monitor introduced adult cattle for evidence of ifection

• tick reduction measures (e.g. dipping - not UK)

• vaccination (not in UK)

Is Leishmania present in the UK?

NO

What are the vertebrate hosts of Leishmania?

• human

• dog

• wild animals

Where is Leishmania found?

• Mediterranean basin

• Africa

• Asia

• Central and South America

What is the vector of Leishmania?

bloodsucking phlebotomine sandfly

What cells of the body does Leishmania infect?

macrophages

What are 2 main forms of Leishmania?

• visceral (humans and dogs)

• cutaneous (humans)

• (and mucocutaneous form in humans)

Is Leishmania a zoonosis?

YES

What species of Leishmania is most common in Europe?

Leishmania infantum

Why is canine leishmaniasis a potential problem in the UK?

• dogs important from southern and eastern europe

• stray dogs brought into UK from endemic countries

What is the incubation period of canine leishmaniasis?

months to years

What are the clinical signs of canine leishmaniasis?

• skin lesions

• ocular abnormalities

• epistaxis

• weight loss

• lethargy

What does this image show?

canine visceral leishmaniasis

Summarise the pathology of canine leishmaniasis

• anaemia

• thrombocytopenia

• hyperglobulinemia

How can you diagnose canine leishmaniasis?

• cytology on Giemsa-stained lymph node or bone marrow aspirates

• PCR

• serology

How can you treat canine leishmaniasis?

• pentavalent antimonials (toxicity) - traditional

• allopurinol

• miltefosine (safer, expensive) - newer

Even if treated, what may happen to dogs suffering from canine leishmaniasis?

• remain carriers

• may relapse

• may remain infectious to sand flies

How can you prevent getting infected with canine leishmaniasis if taking a dog abroad?

• insecticides - topical or impregnated collars

• imidacloprid, deltamethrin

What issues does trypanosomiasis cause?

• anaemia and loss of production in animals

• fatal in humans

• ‘sleeping sickness’