Parasitology - Mammalian Coccidiosis Flashcards
Many species of Eimeria that cause coccidiosis in mammals are:
A. Highly pathogenic
B. Moderately pathogenic
C. Have low pathogenicity
D. Completely harmless
C.
Many species are of little pathogenic importance and high faecal oocyst counts may be found in healthy animals.
Coccidia of cattle:
There are many species but few are of pathological significance in the UK.
Calves less than a year old are sporadically affected.
PPP is 2-3 weeks
What are the two main Eimeria species that cause cocciodiosis in the UK, what are their sites of infection and characteristics of their life cycles?
- E. bovis*
- most common
- big oocysts 28x20 μm
Sites of infection: Central lacteal of small-intestinal villi & epithelial cells of caecum & colon
E. zuernii
- most pathogenic - more blood, morbidity & mortality
- blood-stained dysentery & sloughed mucosa
- spherical oocysts 16 μm
Sites of infection: Connective-tissue cells of lamina propria in lower small intestine & epithelial cells of caecum & colon
What would you use to vaccinate a herd of cattle against coccidiosis caused by Eimeria spp?
Nothing. There are no vaccines available.
What are the clinical signs of bovine coccidiosis?
- *Haemorrhagic typhlocolitis** ie., diarrhoea with pieces of mucosa; bloody diarrhoea
- blood found primarily in large intestine
- continuous need to defecate
- can lead to anal prolapse
- dehydration, anaemia, fever
What are the main Eimeria species that cause cocciodiosis in sheep?
E. ovinoidalis & E. crandalis
Under the microscope, what are the most distinctive feature of Eimeria infection in sheep?
Giant schizonts (macromeronts) visible as white spots
What age of sheep is most susceptibe to coccidial infection?
Lambs ~6 weeks old in mixed groups, esp. twins & triplets
Where are the sites of infection in the lamb by Eimeria species?
Caecum & colon epithelial cells
Why does coccidia in sheep have “enzootic stability”? What does this mean and how can this spread infection?
Ewes are immune carriers, so they contaminate litter, outdoor water & food troughs with oocysts
Early lambs amplify parasite population, later lambs under pressure
However, many lambs with high faecal oocyst counts die before shedding oocysts
What are the two Eimeria species OF IMPORTANCE that cause coccidia in goats? What are the clinical signs of goat coccidia? What are the sites of infection?
- **E. ninakohlyakimovae ***(problem in Portugal)
- E. arloingi*
Clinical signs:
- Diarrhoea
- High mortality & morbidity
- Growth rate retardation
Sites of infection:
Same as Eimeria species in lambs: Caecum and colon epithelial cells
What is the main Eimeria species that causes coccidia in horses? What is its site of infection and what are the clinical signs of disease?
Eimeria leuckarti
Site of infection:
Small intestine - invaded by large gametocytes in subepithelia
Clinical signs:
- occasional diarrhoea
- weight loss
- anorexia
- dehydration
What is different about the horse’s Eimeria leuckarti oocyst and its PPP?
Oocyst is 70 x 53 μm, big & dark, thick oocyst wall
PPP =up to 15 weeks!
What does it mean that E. leuckarti is less immunogenic in the horse than other Eimeria species in other animals?
Infection doesn’t cause development of immunity in affected foals.
What is the most important protozoan that causes coccidiosis in pigs? What is the site of infection and what is the disease? How serious is it?
Isospora suis
Site of infection: Small intestine mucosa (can move to caecum & colon in severe conditions)
Clinical: Profuse diarrhoea, can be fatal
What is the protozoans that causes coccidiosis in dogs and what are the most important species names? What are the sites of infection, and how serious is it?
Protozoa: Isospora & Neospora
Species: Isospora canis, Neospora caninum
Sites of infection: Small intestine
Low pathogenicity: Only occasionally causes disease, so look for other causes of diarrhoea even if faecal oocyst count is high.
What are the differences between the oocysts of Isospora canis and Neospora caninum, which cause canine coccidiosis?
I. canis oocysts are about 60 µm while N. caninum oocysts are only 25-30 µm.
Unlike other protozoan species that cause coccidiosis, Isospora felis of cats has a facultative heteroxenous life cycle. What does that mean?
The protozoan has “choice” of going through wide range of intermediate hosts (rodents, ruminants) in which it can stay in dormant dormozoite state.
What is important about the Isospora felis oocyst in terms of diagnosis?
The oocysts are used to distinguish the protozoan infection from other protozoan invaders such as Toxoplasma gondii & Sarcocystis spp.
The I. felis oocyst is much bigger (about 66 μm) than those of Toxoplasma gondii & Sarcocystis spp
What are the Eimeria species that cause coccidiosis in rabbits? What are the sites of infection, and how serious is the disease?
Eimeria flavascens
Eimeria intestinalis
Site of infection: caecum
- *Intestinal coccidiosis:**
- mucoid diarrhoea, sometimes haemorrhagic
- flatulence
- dehydration
- low appetite
High mortality in cases of severe enteritis
What type of preventative regimen would you recommend against coccidial infection in calves?
- Improve management & hygiene/sanitation; increase bedding, raise water & feed troughs to avoid faecal contamination
- Preventative in-feed anticoccidial drugs:
* decoquinate* - Injectable antiprotozoals eg. sulphamethoxypyridazine might limit oocyst production
- Orally administered coccidiostats: Toltrazuril (Baycox® 5 % Susp., Bayer Health Care); Diclazuril (Vecoxan® 0,25 % Susp., Janssen Animal Health)
- Move animals to clean environment
What type of preventative regimen would you recommend against coccidial infection in sheep?
- Improve management, avoid overcrowding & stress
- Improve hygiene, dag ewes
- Avoid mixing lambs of different ages
- Prevent infection by creep-feeding lambs
with decoquinateororal dosing with diclazuril when lambs are 4-6 weeks. Second dose after three weeks.
What type of preventative regimen would you recommend against coccidial infection in dogs?
Toltrazuril (Baycox® 5% suspension) p.o.
What type of preventative regimen would you recommend against coccidial infection in rabbits?
- Suitable drugs in drinking water:
* Sulfaquinoxalin*
* Sulfadimethoxin* - over 3-5 days, then repeat treatment
* Toltrazuril* - Medicated food can be used in commercial
units
How would you diagnose Eimeria species in a live rabbit?
Float oocysts in salt solution to identify species
Why is it difficult to diagnose coccidiosis in pigs while they’re alive AND after they’re dead?
- Diagnosis difficult ante-mortem because diarrhoea starts before oocysts shed in faeces.
- Difficult @ post mortem because death typically occurs after parasites have left body (it’s self-limiting, like Eimeria)
