5. Cryptosporidiosis, Toxoplasmosis, Besnoitiosis Flashcards
Cryptosporidiosis in mammals
In mammals - Cryptosporidium parvum, C. muris - Zoonosis!
History - many domesticated animal species, especially young calves
Clinical signs
– they depend on parasite and host species, amount of ingested sporulated oocysts, etc.
- mild/sub-clinical infection – no symptoms
- acute diarrhoea or watery/pasty faeces with mucous shreds (exceptionally blood) – in young calves aging 1-3 weeks
- anorexia, fever, dehydration and death – C. parvum
Parasitological diagnosis
- detection of oocysts in samples of faeces with flotation method (e.g. Sheather’ s sugar solution) after straining faeces through appropriate sieve
- it is difficult to distinguish oocysts from other small particles in faeces such as yeast, plant debris, etc.
- most oocysts measure 5-8 µm, appear nearly spherical or elliptical and have obscure internal structures (four sporozoites) → the aid of high resolution microscope → difficulty in species identification
- detection of oocysts in smears of mucosa/faeces or in sections stained with differential staining methods including Kinyoun, Ziehl-Neelsen, safranin-methylene blue stain and Giemsa – they stain oocysts red and counterstain the background – many of these stains require an experienced microscopist, and are labour-intensive
- classical biological characteristics (e.g. host specificity) may be helpful but they are expensive and time consuming
- immunological methods – IF with monoclonal antibodies, ELISA, reverse passive haemagglutination (RPH), etc. – aspecificity of antibody-based methods due to crossreactivity with other microorganisms can be problematic
- molecular techniques – a variety of PCR tests – false positives can result from detection of naked nucleic acids, non-viable microorganisms, and laboratory contamination
Necroscopy findings
- enteral catarrh in ileum
- cellular infiltration of propria with cryptosporidium stages (on the microvillous brush border of epithelial cells) by light microscopy and EM
- above mentioned disorders in digestive glands of abomasum – C. muris
Cryptosporidiosis in Birds
C. baileyi, C. meleagridis
History - many species, especially young chickens
Clinical signs
– they depend on parasite and host species, amount of ingested sporulated oocysts, etc.
- mild/sub-clinical infection – no symptoms
- signs of respiratory disease (coughing, sneezing, dyspnoea, nasal discharges, conjunctivitis) – infection via air
- rarely diarrhoea
Parasitological diagnosis as in mammals
Necroscopy findings
- signs of inflammation of the air sacs, pneumonia, sinusitis
- histological changes may occur in small and large intestine, cloaca and bursa Fabricius and/or in trachea, bronchia, rarely in kidneys
Toxoplasmosis
Toxoplasma gondii - Zoonosis
History
- final hosts – species of Felidae
- intermediate hosts – lots of mammal and bird species
Clinical signs
- infection is usually latent without any clinical signs
- are related to affected organ (eyes, CNS, heart)
- in cat rarely encephalitis, enteritis, pneumonia
- in dog rarely anorexia, diarrhoea, pneumonia, CNS symptoms
- in horse rarely nervous signs (e.g. impaired vision)
- in pregnant ewes abortion frequently occurs in the first half of gestation or foetus may be still-born/weak
- in swine rarely fever, apathy, diarrhoea, respiratory distress and CNS symptoms may occur during the acute phase; pregnant sows may abort or farrow weak or still-born pigs
- in pregnant women - abortion, premature delivery, still-birth, mental disorders, blindness of the new-born
Parasitological diagnosis
- detection of unsporulated oocysts (ca 10x12 μm) with flotation method - only in cat faeces! patency max. 20 days (1-2 weeks)
sporulated oocysts have 2 sporocysts containing 4 sporozoites each - indistinguishable from oocysts of Hammondia hammondi
- immunodiagnostic methods
Sabin-Feldman dye test - specific antibodies disable staining tachyzoites by methylene blue
Complement Fixation Test – less reliable with bovine, swine and poultry
ELISA, IHAT (except for swine), IFAT
- demonstration of toxoplasms (tachyzoites, cysts (20-100 μm, round, thin-walled)) in samples of biopsy, cerebrospinal fluids by staining or IFAT
- tissue culture
- mouse inoculation test – tachyzoites in ascites after 5-10 days, cysts in brain in 20-30 days except for “RH” strains which do not form cyst and kill all infected mice within 4-7 days after infection
- modern methods in humans
PCR from human cerebrospinal fluids
neuroimaging and thallium-201 brain single-photon emission CT
Necroscopy findings
– they are related to extra-intestinal development
- aborted foetus of sheep and goat may be retained or mummified; numerous yellowishwhite necrotic spots (1-2 mm in diameter) in placenta, lymphocytic infiltration of brain
- necrotic foci and granulomas in liver, spleen, lungs, brain, etc. of rabbits - disseminated toxoplasmosis
- disseminated toxoplasmosis in young dogs in conjunction with Rubarth’s disease, canine distemper, etc. – necrotic and inflammatory foci with cysts in organs
- very rarely - pneumonia, enlarged mesenteric lymph nodes, encephalitis
Besnoitiosis of Cattle
Causative agent:
- Besnoitia besnoiti (heteroxenous)
- cattle is intermediate host (wild ruminants also susceptible), final host unknown
- cystozoites can be transmitted mechanicallyby blood sucking flies(Tabanus, Stomoxys)
Clinical signs:
- in the majority of cattle asymptomatic
- acute: anorexia, fever, swollen lymph nodes, rhinitis, dyspnoea, subcutaneous oedema (head, limbs)
- chronic: skin thickening, wrinkling, alopecia
- abortion in cows, sterility in bulls (infection of testes)
Parasitological diagnosis:
- cysts in the sclera (pathognomic), conjunctiva, mucosa of respiratory and genital organs
- biopsy of skin
- serology (PrioCheck ELISA; for confirmation of the results: Western blot, IFAT)
Necropsy findings
- macroscopically visible cysts (up to 6-800 m) on the serosal, mucosal surfaces
- histology: inner layer of cyst wall thin (nuclei), outer thick (homogenous)
