Week 2 - Protozoa 1 & 2

Toxoplasma gondii

Important cause of abortion and perinatal mortality in sheep

Toxoplasma gondii life cycle

• Final host cat - infected by ingestion of infected tissue

• Bradyzoites released invade gut epithelial cells - multiply

• Oocyst in gut shed in feces

• Oocyst becomes infective by sporulating (within 24hrs at 25C w/ moisture)

• Sporulated oocyst ingested by intermediate host - sporozoites released invade gut cells

• Form tachyzoites - multiply fast - released as cell gets destroyed - infects more cells

• Immune response kicks in, tachyzoites controlled

• Tachyzoites evade immune response by forming bradyzoites - generate a cyst in tissues

Toxoplasma gondii transmission pathways

Cat - cat feces - food contaminated w/ sporulated oocytes - oocytes ingested through food/water - intermediate hosts - ingestion of tissue cysts in uncooked meat

Neospora caninum

Important cause of abortion and perinatal disease in cattle

Neospora caninum life cycle

• Dog is final host - sexual phase occurs in intestinal epithelium - oocytes in feces

• Oocytes sporulate & become infectious

• Bovine infected by ingestion of feed

• Sporozoites released, infect cells, form tachyzoite, rapid multiply and infect more cells

• Immune response causes tachyzoites to form bradyzoites within cyst wall in tissues

Tritrichomonas fetus

Low grade inflammation of endometrium, the inner lining of the uterus - leads to abortion

Eimeria in poultry

• Intracellular parasite

• Infects gut epithelium

• Fecal - oral transmission

• Severity of clinical presentation directly related to the infective dose

Species of Eimeria in chickens

• E. tenella

• E. brunetti

• E. necatrix

• E. maxima

• E. mitis

• E. acervulina

• E. praecox

Goes high to low pathogenicity

(These Birds Need Maximal Motherly Attention Perhaps)

Eimeria pathogenesis

• Destruction of gut epithelial cells

• Villous atrophy

• Malabsorption of nutrients - limited weight gain/loss of egg production

• Reduced feed conversion

• Diarrhoea

• Hemorrhage into lumen of intestine - blood loss

• Death - in severe cases

Eimeria diagnosis

1. Appearance of bird

2. Abnormal feces

3. Lab detection of oocytes in feces

4. Post mortem bird

Eimeria epidemiology (what causes disease)

• Age

• Previous exposure

• Genetics

• Diet

• Hygiene

• Litter management

• Rearing system

Eimeria control

• Hygiene & biosecurity

• Anticoccidals in feed

• Vaccines

Bovine coccidiosis

• Infection not always associated with clinical disease

• Low infective dose

• Animals may experience weight loss or decreased weight gain

• After infection the animal becomes immune to that particular Eimeria sp.

• Normally only found in younger animals (1m - 1y)

Sheep coccidiosis

• E. ovinoidalis & E. crandallis

• Ileum, cecum, and upper colon affected

• Clinical signs: diarrhea, weight loss, anemia, dehydration

• Common in lambs 1-2 mo

Goat coccidiosis

• E. arloingi & E. christenseni

• Pathogenesis, epidemiology, & control similar to sheep

Rabbit coccidiosis

• Most pathogenic in intestine: E. flavescenes & E. intestinalis

• Liver: E. stiedae

• Destruction of intestinal crypts

• Clinical signs: Diarrhea, reduced appetitie, emaciation

• Young rabbits most at risk. Asymptomatic rabbits still carry disease

Isospora spp - Significant species

• Cats: I. felis & I. rivolta

• Dogs: I. canis & I. ohioensis (3 types)

• Pigs: I. suis

Isospora in cats and dogs

• Puppies & kittens <6 mo

• Adults immune but carriers

• Clinical signs: diarrhea, vomiting, dehydration, weight loss

• Treatment: Sulphonamides

• Control: good hygiene standards in kennels & catteries

Isospora suis in pigs

• Affects nursing piglets (8-15 days old)

• Adults immune but carriers - infection occurs more from contaminated farrowing crate

• Clinical signs: diarrhea, dehydration, failure to thrive

• Mortality <20%

• Control: cleaning farrowing crates, burning bedding

Cryptosporidium

• Main species: C. parvum (zoonotic) - hard to diagnose

• Causes: villus atrophy, epithelial cell destruction, malabsorption, diarrhea

• Transmission: fecal/oral, water/food-borne

• Oocysts do NOT contain sporocysts

• High prevalence of infection

• Treatment: Good husbandry, removed calves from dam at birth, avoid overcrowding