Author
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Fayer, Ronald |
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Trout, James |
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Jenkins, Mark |
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Gasbarre, Louis |
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Submitted to: Beef Cattle Research Field Day
Publication Type: Abstract Only Publication Acceptance Date: 10/6/1999 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: The immune system of newborn calves was studied to determine how well it responded to C. parvum infection. Young calves were found to lack most of the intestinal immune cells commonly found in older animals; this helps to explain the high susceptibility of calves to infection. Newborn calves receive passive immune protection in the colostrum; thus, immunizing cows against C. parvum may enable them to pass this immunity to their offspring Various C. parvum antigens and immunization protocols were evaluated. A direct DNA immunization of cows was found to produce high levels of antibodies in the colostrum. A mouse model using polymerase chain reaction (PCR) based detection of C. parvum infection was developed for preliminary testing of the colostrum. The results indicated that this colostrum reduced the levels of infection in mice. Testing in calves is currently underway. Exposure of C. parvum to x-rays weakens them so that they are unable to complete their life cycle. After preliminary testing in the mouse model, trials are underway in calves to determine if these attenuated parasites can stimulate immunity without causing a clinical infection. Wild rodent droppings have tested positive for C. parvum oocysts. Thus, rodents are a potential source of infection. Although birds are not infected by C. parvum, it was discovered that C. parvum oocysts fed to birds emerge in the bird feces and are still infectious. Additonally fecal samples collected from wild Canada Geese were fund to containonally infectious C. parvum oocysts. Thus, as birds peck through manure looking for undigested seeds and grain, they can ingest oocysts and potentially transmit them from farm to farm as mechanical vectors. Studies on the |
