3+4. Coccidiosis Flashcards
General morphology of Eimeria spp.
unsporulated and sporulated oocyst
- 15-50 µm size, ellipsoidal, ovoid or spherical shape
- refractive shell, micropyle (a small pore) covered with a polar cap
- nucleated mass of protoplasm (zygote) within the shell - in an unsporulated oocyst
- 4 sporocysts each containing 2 banana-shaped sporozoites, residual body in oocyst and in sporocyst – in a sporulated oocyst
schizont – can reach 300 µm in diameter (macroschizont or globidium)
merozoite - 5.0-10 µm long, crescent shaped
Coccidiosis of chicken
History - usually in flocks aging 3-6 weeks, in breeder and layer replacement stocks aging 10-14 weeks
Clinical signs
– they depend on species, amount of ingested sporulated oocysts, virulence of species, resistance of hosts, etc.
- anorexia, moribund appearance with lethargy, ruffled feathers; loss of skin pigmentation; soft faeces often containing blood, succumb within 1-2 days after first signs – caused by E. tenella, E. necatrix, E. brunetti
- droop, watery diarrhoea, reduced weight gain, reduced egg production – caused by other species
- mild/sub-clinical infection – unnoticed
Parasitological diagnosis
- detection of unsporulated oocysts in samples of faeces and/or litter with flotation method
- except for oocysts of E. maxima (30x20 µm) oocysts of other species are not characteristics to identify species
- species identification of oocysts - sporulation time, size and shape of sporulated oocysts, isoenzyme patterns, PCR, etc. – not for routine diagnosis
- oocyst counting (OPG) with McMaster method – no correlation between pathological changes in the gut and oocyst shedding!
- a bird may harbour more than one species!
Necroscopy findings
- post-mortem examination is the most important!
- they depend on species, amount of ingested oocysts, virulence of species, resistance of hosts, etc.
- the location and type of lesions usually provide a good guide to the species identification
- scoring lesions of intestine after extermination
- microscopic study of scrapings of the intestinal mucous membrane (schizonts, gamonts, unsporulated oocysts) – may be diluted with saline on a slide and covered with coverslip
- histological findings of intestine
Coccidiosis of chicken
- species
E. tenella
– extensive haemorrhages in caecum, unclotted, partially clotted or clotted blood in lumen; dilation and thickening of the wall; deep erosion of epithelium;
- schizonts and free merozoites in smears from the caecum mucosa
- acute death without the presence of oocysts may occur
- in longer-standing infections caseous material in the lumen which adheres to the mucosa
E. necatrix
– the wall of the middle third of the small intestine (jejunum and ileum) is haemorrhagic, thickened, swollen; unclotted blood in lumen; scattered white 6 spots – they may be seen through the serosa (“pepper and salt”)
- large schizonts (60-70 µm in diameter) in scrapings of mucosa
E. brunetti
– lower small intestine, prox. caecum, colon, rectum, cloaca
– haemorrhagic, catarrhal exsudate and coagulative necrosis of the mucosal surface; sometimes petechiae are on the tip of villi in the rectum – ladder-like appearance
E. maxima – the mid-small intestine – inflamed, ballooned, slack; mucosa is thickened; petechiae are on serosa and mucosa; slightly orange/salmon pink exudates in lumen
- large yellowish oocysts or gametocytes may be seen in scrapings of mucosa
E. acervulina
– duodenum (and jejunum)
– visible (1-2 mm) discrete white foci or transverse bands which are ladder-like; the contents of lumen are watery – only in heavily infected animals
E. mitis, E. praecox – no macroscopic lesions
Coccidioses of Geese
Intestinal coccidiosis - E. anseris, E. nocens
History: usually in 2-3 month old geese
Clinical signs
- anorexia, polydipsia, weakness, unstable gait, profuse diarrhoea (death)
Parasitological diagnosis
- detection of unsporulated oocysts in the faeces (with flotation)
Necroscopy findings
- middle to lower third of the small intestine distended, filled with reddish brown fluid
- mucosa hyperaemic, catarrhal, with capillary haemorrhages, fibrinous-diphtheroid enteritis
Renal coccidiosis - E. truncata
Clinical signs
- acute course: weakness, anorexia, diarrhoea, sunken eyes, disturbances in balance (vertigo), torticollis, lying supine, sometimes paralysis
Parasitological diagnosis
- detection of unsporulated oocysts in the faeces (with flotation)
Necroscopy findings
- kidneys are enlarged, greyish yellow or yellowish red, on the surface and cut surface pin-prick to pinhead size greyish white foci (urate salts) histology: distended renal tubules, tubulonephrosis, interstitial nephritis
Coccidiosis of Cattle
Coccidiosis of cattle – 21 species of Eimeria of which E. zuernii and E. bovis are the most pathogenic
History: usually in calves aging 2-6 months, kept under crowded and unsanitary conditions, mainly in feed lots and yards; after stressful events (weaning, a change of feed, etc.)
- rarely in yearlings and adults
Clinical signs
– they depend on species, amount of ingested sporulated oocysts, virulence of species, resistance of hosts, etc.
- mild infection – unnoticed
- anorexia, fever, haemorrhagic and viscous diarrhoea – mucous shreds or blood in faeces
- anaemia, dehydration, progressive weight loss, cachexy, tenesmus, rectal prolapse
- death can occur rapidly, mainly in calves
- rarely cerebral disorders - tetanic convulsions, nystagmus, etc.
Parasitological diagnosis
- detection of unsporulated oocysts in samples of faeces with flotation method It is not enough to detect any oocysts!
- little difficulty should be encountered in identifying the different species but size ranges can lead to confusion between some species – measurement of a few oocysts
- schizonts and merozoites in mucous and/or bloody shreds of faeces – E. zuernii
- oocyst counting (OPG) with McMaster method - no correlation between pathological changes in the gut and oocyst shedding! - large numbers of oocysts of pathogenic species in the faeces
- animals usually harbour more than one species and excrete a few oocysts!
Necroscopy findings
- they depend on species, amount of ingested oocysts, virulence of species, resistance of hosts, etc.
- catarrhal to diphteriod enteritis in large intestine (terminal ileum, caecum and colon) – mucosal oedema, diffuse haemorrhages
- microscopic study of scrapings of the intestinal mucous membrane
- histological studies - desquamation of mucous membrane, necrosis of epithelial tissue, various stages of coccidia, etc.
Coccidioses of Rabbit
Coccidioses of rabbit – two forms: biliary and intestinal
Biliary coccidioses of Rabbit
E. stiedai
History - usually after weaning, at age of 1-2 months
Clinical signs
- usually sub-clinical infection – no symptoms
- anorexia, digestional problems, wasting, polyuria, meteorism, jaundice
Parasitological diagnosis
- detection of unsporulated oocysts in samples of faeces with flotation method It is not enough to detect any oocysts! Differentiation from intestinal coccidia - not for routine diagnosis!
- large (37x21µm) elliptical oocyst
Necroscopy findings
- hepatomegaly, greyish yellow nodules in liver (cirrhosis)
- microscopic study of smears taken from hepatic lesions filled with pus or caseous material – gamonts and unsporulated oocysts
- histological studies – biliary hyperplasia, cholangitis, distention of bile ducts, gamonts, unsporulated oocysts
Intestinal coccidiosis of Rabbit
10 species of Eimeria of which E. intestinalis and E. flavescens are the most pathogenic
History - usually after weaning, at age of 1-2 months
Clinical signs
- they depend on species, amount of ingested sporulated oocysts, virulence of species, age of hosts, etc.
- usually sub-clinical infection – no symptoms
- anorexia, increased water consumption, weight loss, emaciation
- mild intermittent to severe diarrhoea which may contain mucous or blood, dehydration, death within a few days
Parasitological diagnosis
- detection of unsporulated oocysts in samples of faeces with flotation method It is not enough to detect any oocysts! Identification of species - not for routine diagnosis!
- usefulness of OPG
Necroscopy findings
- catarrhal and/or haemorrhagic enteritis, thickening of mucosa in small intestine (E. intestinalis, E. magna, E. irresidua) or in large intestine (E. flavescens, E. piriformis)
- pinhead size white nodules in ileum – E. magna
- microscopic study of scrapings of the intestinal mucous membrane – coccidian stages
- histological studies - desquamation of mucous membrane, necrosis of epithelial tissue, various stages of coccidia, etc.
Coccidiosis of Pig
History - usually between 8-15 days of age
Clinical signs
- the main clinical symptom is diarrhoea
- scours range from white to yellow in colour and pasty to watery in consistency, blood is never present
- severely affected nursing piglets become dehydrated
Parasitological diagnosis
- direct examination of faecal smears for unsporulated oocysts is not very sensitiv
- detection of sporulated oocysts by flotation technique after sporulation
- autofluorescence microscopy increases the sensitivity of detection
- sporulated oocysts of I. suis are spherical, measuring about 20 μm in diameter with smooth oocyst wall – two sporocysts containing four sporozoites each
Necroscopy findings
- lesions in the mucosa of the small intestine (jejunum and ileum)
- microscopic exaination of scrapings taken from mucosa of small intestine - number of developmental stages
Coccidiosis of Carnivores
History - in young dogs and cats mainly in crowded breeding kennels with unhygenic conditions
Clinical signs
- mainly sub-clinical infestation without any symptoms 9
- diarrhoea (lasts for 1-2 days in kittens and for 1-2 weeks in puppies), emaciation, anaemia, dehydration, exsiccosis
Parasitological diagnosis
- detection of unsporulated oocysts by flotation technique
- identification of species may be easy in cat and dog :
in cat: Isosopra felis – oval oocysts (ca 42 μm), I. rivolta – (26 μm)
in dog: I. canis (38 μm), I. ohioensis (25 μm), I. burrowsi (20 μm)
to be distinguished from other oocysts/sporocysts in the faeces:
in cat: Toxoplasma gondii, Hammondia hammondi (oocysts are ca 12 μm) , Sarcocystis spp.
in dog: Neospora caninum, Hammondia heydorni (oocysts are ca 12 μm), Sarcocystis spp.
Necroscopy findings
- catarrhal or haemorrhagic enteritis
- microscopic examination of scrapings taken from mucosa of small intestine - number of developmental stages
