Diarrhea in Calves Induced by Cryptosporidium parvum

Diarrhea is a common manifestation of intestinal/ systemic homeostatic altera-tion in neonatal calves, lambs, and kids.  Neonatal diarrhea may cause acute dehydration and death or lead to malnutrition and emaciation.  Crypto-sporidium parvum is highly infectious and highly resistant to inactivation in the environment.  There is no routinely successful form of therapy available.  There is also a zoonotic implication in humans handling the animals, especially in immunocompromised humans.

Etiology and Pathogenesis: Neonatal calf diarrhea usually involves the association of more than one pathogen.  The most common implicated pathogens are E. coli, rotavirus, coronavirus, and Cryptosporidium parvum.  Cryptosporidium parvum (disease name Crypto-sporidiosis) is a protozoan parasite transmitted by fecal-oral contamination.  These protozoa invade the apical surface (brush border) of the enterocyte in the distal small intestine and proximal colon and form parasitophorus vacuoles where development occurs.  Infection results in crypt and submucosal inflammation, necrosis of microvilli, villous atrophy, and decreased mucosal enzyme activity.  This results in decreased absorptive ability of the intestinal tract, fermentation of nutrients within the lumen, and osmotic diarrhea.

Life cycle:  Infection begins by ingestion of oocysts from feces.  These oocysts contain four sporozoites and initiate infection following excystation.  The organism replicates asexually and then sexually to produce new oocysts that are shed into the environment in feces or reinfect the host.  The definitive hosts include many mammals such as cattle, dogs, cats, and humans.

Epidemiology:   C. parvum oocysts are commonly found in the feces of healthy calves.  The cause of diarrhea depends on multiple factors such as the degree of virulence of the pathogenic strain, the presence of more than one pathologic agent, and the success of passive transfer of colostral immunoglobulins.  Calves with low immunity are highly susceptible to enteropathogenic infections leading to severe and often fatal diarrhea.  Also, the lack of specific antibodies in the dam and the use of specific vaccines may interfere in the immunoglobulin transfer to the calf.  Stress factors, poor environmental conditions, exposure to contaminated maternal feces as well as feces from healthy calves, and inappropriate diet also increase the risk for disease.  Transmission is by fecal-oral contact and fecal aerosol.

Diagnostics:  Fecal samples from untreated calves should be submitted during  early diarrheic stages.  Sugar flotation can be performed to identify the oocysts.  Bacteriology and virology cultures can be performed to verify the presence of other agents.  The microbiologic interpretation may be difficult because of mixed infection and because some potential enteropathogens are commonly present in healthy calves.  Ideally, live representative calves should be presented for necropsy examination so that fresh intestinal sections can be prepared to identify the presence of organisms at the surface of epithelial cells.

Treatment:  There is no effective chemo-therapeutic agent for routine treatment of cryptosporidiosis, but supportive care is recommended.  Paromycin has been used with limited success in cats and human patients, but its efficacy in other species has not been determined.  Oral Bovine Serum concentrate has been used in calves with experimentally induced cryptosporidiosis.  Hunt and Armstrong determined that there was a 33% reduction in the volume of diarrhea at the peak of illness, 30% reduction in intestinal permeability, and enhanced ideal crypt depth and villous surface area, as compared to untreated, infected calves.

Prevention and control:  Good hygiene during management of the entire herd is important in reducing the incidence of cryptosporidiosis.  Isolation of sick calves to a separate area to reduce contamination is also important.  The dam and calf should be provided good nutrition, and administration of high quality colostrum within the first six hours of birth helps reduce infection.

-by Jorge Araque, ECFVG Student

-edited by Dr. Michael Owston, ADDL Graduate Student

References:

1. Holland RE: 1990.  Some infectious causes of diarrhea in young farm animals.  Clin Microbiol Rev 3:345-75.

2. Harp JA, Goff, JP: 1995.  Protection of calves with vaccine against Cryptosporidium parvum. J Parasitol 81:54-57.

3. Hunt E,  Fu Q, Armstrong MU: 2002.  Oral Bovine Serum Concentrate Improves Crypto-sporidial Enteritis in Calves.  Pediatric Res 51:370-376.

4. www.cal.vet.upenn.edu/dxendopar/ parasitepages  protozoa/c_parvum.htm

5. www.cal.vet.upenn.edu/dxendopar/ techniques/comfecal.html

6. www.merckvetmanual.com/mvm

7. www.vetmed.wisc.edu/pbs/zoonoses/ Glk9fel/crypto.html