الفهرس 
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Abstract
The study showed that cryptosporidium infection was detected in Friesian calves and buffalo calves in Behera province. The oocysts were passed with the faeces fully sporulated. They were spherical to ovoid in shape and measured 3.7-5.4 x 4.5-5.6 Urn (mean: 4.6 x 5.4 Urn). The present study showed that 95 (31.67%), 103 (34.33%) and 94 (31.33%) out of 300 Friesian calves collected during the period of December 1998 to November 1999 were infected with cryptosporidium by the use of modified Ziehl-Neelsen technique, safranin methylene blue and modified trichrome stain respectively. Also this study clarified that out of 280 buffalo calves collected during the same period 56 (20%), 58 (20.71%) and 54 (19.3%) had cryptosporidium by the used three staining method respectively. The comparative study between the three different staining methods in diagnosis of cryptosporidia showed that the three different stains were nearly equivalent in diagnosis of cryptosporidia.
Clinical examination of investigated calves revealed presence of watery yellow faces (may contain blood or mucous) or normal faeces beside tenesmus anorexia, depression, colic and fever. Concerning the monthly variation of cryptosporidia infection on using of modified Ziehl-Neelsen technique, it was found that high rate of cryptosporidium infection was recorded in August (59.37%),
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April (54.54%\ and March (47.72%). The lower rate of infection was recorded in September 1999 to February 1999 (11.90%-13.04%). The seasonal variation showed that the highest rate of infection was recorded in summer (47.43%) followed by spring (41.89%), autumn (18.34%) and winter (17.94%).
The study showed that cryptosporidiosis is a disease of young calves as 41.41%, 40%, 30.62% and 10.23% of Friesian calves aged up to 10 days, 11-19 days, 20-29 days and 1-3 months infected with cryptosporidium respeOtively. Also, 27.85%, 23.53%, 22.58% and 5.63% of buffalo cal’ifes aged up to 10 days, 11-19 days, 20-29 days and 1-3 months had cryptosporidia respectively.
The study revealed that the incidence of infection among diarrhoeic calves of less than one month was 53.54% and 21.62% in calves aged 1-3 months While in apparently healthy calves the infection was 7.01% and 3.2% in calves aged less than one month and 1-3 months respectively. In addition, the incidence in buffalo calves was 32.87% and 8.111% in diarrhoeic buffalo calves aged less than one month and 1-3 months respectively. While in non diarrhoeic buffalo calves the incidence was 4.76% and 2.94% in buffalo calves aged less than one mar an.. 1-3 m iths respectively.
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Experimental infection of mice using the cryptosporidium oocysts separated from the faeces of infected calves was conducted. One group of infected mice with cryptosporidium oocysts was treated with ivermectin only and other group of mice was treated with combination of ivermectin and gentamycin sulphate. Parasitological examination of faecal samples of the infected group revealed the presence of cryptosporidium oocysts and the mean count was 18.4 ± 7.7. The histopathological findings revealed changes of jejunum and ileum of the infected group where there were fusion, broadening and shortening of the villi in many mucosal areas and the mucosa showed denudation with sloughing of the brush border which was studded with cryptosporidial organisms, also there was mononuclear cellular infiltration in the lamina propria (histocytes, neutrophils and lymphocytes) and the mean count of cryptosporidium organisms in the small intestinal sections of infected mice were 16 ± 8.4.
No cryptosporidial oocyst was detected in the faeces of two subgroups of mice treated with ivermectin only or ivermectin gentamycin sulphate combination. There was marked improvement in the histopathological changes of ivermectin treated mice in the form of minimal denudation of the covering epithelium, very few organisms were hardly seen, moderate cellular infiltration in the lamina propria and fusion of villi in some areas. Also the pathological changes were more improved in ivermectin
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gentamycin sulphate treated mice where the mucosa appeared roughly normal with only minimal denudation at apices of villi, the cryptosporidium organisms were scanty, fusion of villi was not more seen and some inflammatory cells were still present. The mean number of cryptosporidium organisms/oil immersion filed in the small intestinal sectiOns in ivermectin treated mice and ivermectin gentamycin sulphate treated mice were 1.5 ± 0.5 and 1.4
± 0.6 respectively.
In naturally infected calves, the mean count of cryptosporidium oocysts in their faeces was 34.6 ± 15.9. After treatment with ivermectin only or ivermectin gentamycin sulphate combination no oocysts were detected in their faeces. The clinical improvement of the diseases calves after treatment declared that the group of calves treated with combination of ivermectin-gentamycin sulphate exhibited marked improvement in clinical signs than in group treated with ivermectin only.
Further investigations are still needed to declare the exact mechanism of anticryptosporidial action of ivermectin.