Cryptosporidium is a protozoa in the Phylum Apicomplexa Cryptosporidium Parvum genotype 1

Transcription

1 September, 2010

2 Cryptosporidium is a protozoa in the Phylum Apicomplexa Cryptosporidium Parvum genotype 1 Livestock not commonly infected but can occur through contamination of feeds by other species, etc. Zoonotic Cryptosporidium Parvum genotype 2 Infects cattle, small ruminants, horses, pigs Zoonotic Cryptosporidium andersoni Infects cattle Little evidence that infection is associated with disease

3 life_cycle_lrg.htm

4 Autoinfection Thin-walled oocysts are released into the gut lumen and are able to initiate a new life cycle within the current host Sporulated oocysts are shed Immediately infective unlike Eimeria spp. Small infective dose required Large numbers of oocysts excreted environmental contamination possible heavy

5 Common infection of pre-weaned calves NAHMS National Dairy Heifer Evaluation Project ( ) Survey of 1811 farms in 28 States At any one time, 22% of pre-weaned heifers are shedding Estimated that >90% of farms are infected Prevalence of shedding influenced by farm size <100 cows approx. 80% >100 cows nearly every calf ALMOST EVERY LARGE HERD WILL BE CRYPTO POSITIVE!!

6 76% of farms were found to have at least one infected calf 40.6% of calves (203/500) were shedding oocysts at time of fecal sampling Within-herd prevalence ranged from 0% to 72% Trotz-Williams et al. (2005)

7 Failure of passive transfer Inadequate nutrition Cold stress/chilling Group housing of pre-weaned calves Poor environmental hygiene Oocysts resistant to most disinfectants Oocysts can survive for upwards of 18 months in cool, wet conditions as well as in soil and slurry

8 Fecal-oral transmission Pre-patent period = 2-7 days Infection occurs along the brush border of the small intestine Cell damage leads to villous atrophy and hyperplastic crypt cells Malabsorptive Diarrhea Sheds oocysts in feces for 3-12 days.

9 There are no characteristic signs that distinguish cryptosporidiosis from other causes of calf scours. Asymptomatic infections possible 5 to 35 days of age Most commonly between 7-21 days Mild to moderate diarrhea Yellow or pale, watery feces containing mucus Persists for several days regardless of treatment ± Loss of body weight or emaciation Variable feed intake & dehydration

10 Rotavirus (5-15 days of age) Coronavirus (5-21 days) Giardia (10-30 days) Attaching and Effacing E. Coli (20-30 days) BVD (14-30 days +) Eimeria spp. (>30 days) Salmonella (5-42 days) Clostridium perfringens types B & C (5-15 days) Radostits p. 849 CONCURRENT INFECTIONS WITH ROTAVIRUS AND/OR CORONAVIRUS ARE COMMON!

11 Detection of oocysts in feces Giemsa stain on fecal smears Sucrose Flotation Need oocysts/ml feces to be diagnostic Necropsy Gross: Variable dehydration, emaciation, serous atrophy Yellow/pale, watery intestinal content Histologically: Villous atrophy of small intestine Large #s of protozoa located along/embedded within brush border of small intestine

12 Do NOT withhold milk Higher case fatality rate observed when do Oral electrolytes Can offer/tube 2L at noon if feeding milk in morning and evening Intravenous fluids as required Keep warm and dry

13 Halofuginone (Halicure) Available in Canada via Emergency Drug Release µg/kg BW per os SID for 7 days starting at 1 day of age Does not prevent infection but does reduce the severity of clinical disease Reduces magnitude of oocyst shedding Prevents autoinfection?? Antibiotics are not effective

14 Usually self-limiting Otherwise healthy calves will recover spontaneously in 5-10 days Case fatality rate tends to be low unless complicating factors present concurrent infections inadequate colostrum and/or milk intakes cold stress Will develop natural immunity Shedding less common but may intermittently occur in older animals (e.g. at calving)

15 Infectivity of the oocysts destroyed by: Temperatures <0 C (32 F) and >65 C (149 F) Ammonium hydroxide Hydrogen peroxide Chlorine dioxide 10% formalin saline 5% ammonia

16 Remove from calving environment ASAP Peri-parturient rise in oocyst shedding can occur Good colostrum management practices to reduce incidence of concurrent infections Note that crypto immunity is not based on circulating IgG levels but rather high titres locally within the gut lumen Providing ample nutrients to support immune function Cell-mediated immunity needed to clear infection Individual housing of pre-weaned calves If not present, isolate sick calves from group pens Excellent hygiene in calf area Pressure wash hutches/pens between uses to remove gross fecal contamination Move hutches to a new spot as often as possible Individual bottles/pails or wash with appropriate disinfectant after each feeding Handle/work with scouring calves last Rodent and fly control

17 Radostits, O.M., C.C. Gay, K.W. Hinchcliff, P.D. Constable. Veterinary Medicine 10 th Edition. Pp 849, Merck Veterinary Manual htm Quigley, J. Calf Note #12: Cryptosporidium and Cryptosporidiosis NAHMS, USDA. National Dairy Heifer Evaluation Project: Cryptosporidium is common in dairy calves. Trotz-Williams, L.A., B.D. Jarvie, S.W. Martin, K.E. Leslie, A.S. Peregrine. Prevalence of Cryptosporidium parvum infection in southwestern Ontario and its association with diarrhea in neonatal dairy calves. Can Vet J April; 46(4):