Description of fecal shedding of Cryptosporidium parvum oocysts in experimentally challenged dairy calves

The objective was to describe the probability of Cryptosporidium parvum fecal oocyst shedding at different magnitudes of exposure, the pattern of fecal shedding over time, and factors affecting fecal shedding in dairy calves. Within the first 24 h of life, 36 calves were experimentally challenged with C. parvum oocysts at one of four possible magnitudes of oral exposure (1 × 10³, 1 × 10⁴, 1 × 10⁵, and 1 × 10⁶ oocysts), and 7 control calves were sham dosed. Fecal shedding occurred in 33 (91.7 %) experimentally challenged calves and in none of the control calves. There was a difference in the log-total number of oocysts counted per gram of feces dry weight among the four exposure groups; calves with the lowest magnitude of exposure (1 × 10³ oocysts) shed less than the other three groups. At higher magnitudes of exposure, there was more variability in the range of fecal oocyst shedding. There was an inverse relationship between the log-total amount of oocysts counted per gram of feces dry weight and the number of days to the onset of fecal shedding per calf, i.e., the more time that elapsed to the onset of fecal shedding, the fewer oocysts that were shed. The pattern of fecal shedding over time for all calves shedding oocysts was curvilinear; the number of oocysts increased with time, reached a peak, and declined. Therefore, the dynamics of oocyst shedding can be influenced in part by limiting exposure among calves and delaying the onset of fecal oocyst shedding.

Serological survey of Toxoplasma gondii, Dirofilaria immitis, Feline Immunodeficiency Virus (FIV) and Feline Leukemia Virus (FeLV) infections in pet cats in Bangkok and vicinities, Thailand

The seroprevalence of Toxoplasma gondii, Dirofilaria immitis (heartworm), feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) infections was examined using serum or plasma samples from 746 pet cats collected between May and July 2009 from clinics and hospitals located in and around Bangkok, Thailand. The samples were tested for heartworm, FIV, and FeLV using a commercial ELISA. Of the 746 samples, 4.6% (34/746) were positive for heartworm antigen, 24.5% (183/746) had circulating FeLV antigen, and 20.1% (150/746) had antibodies against FIV. In addition, the first 348 submitted samples were tested for T. gondii antibodies using a modified agglutination test (MAT, cut off 1:25); 10.1% (35/348) were seropositive. Of the 348 cats sampled for all four pathogens, 11, 10, and 1 were positive for T. gondii antibodies and FIV antibodies, FeLV antigen, or D. immitis antigen, respectively. Of the 35 T. gondii-seropositive cats, 42.9% (15/35) were co-infected with at least one of the other three pathogens. The presence of antibodies to FIV was significantly associated with both age and gender, while FeLV antigen presence was only associated with age. In the case of FIV, males were twice as likely to be infected as females, and cats over 10 years of age were 13.5 times more likely to be infected than cats less than 1 year of age. FeLV antigen was more common in younger cats, with cats over 10 years of age being 10 times less likely to be FeLV positive than cats under 1 year of age. This is the first survey for these four pathogens affecting feline health in Thailand.

A comparison of fecal percent dry matter and number of Cryptosporidium parvum oocysts shed to observational fecal consistency scoring in dairy calves

Evaluation of dairy calf feces is often used in research and for clinical decision making to assess severity of diarrhea. However, this has not been validated for agreement between dry matter content and observed fecal consistency. Therefore, a comparison of observed fecal consistency score to fecal percent dry matter and Cryptosporidium parvum oocyst shedding was performed to assess the accuracy of observational scoring as a measure of diarrhea and its association with number of oocysts shed. Fecal samples from 20 dairy calves experimentally infected with C. parvum oocysts were collected daily post-infection and scored on a scale from 1 to 4, with 1 being normal feces to 4 being severe diarrhea. An aliquot of each sample was analyzed for percent dry matter and Cryptosporidium oocyst counts by using immunofluorescent microscopy. Fecal consistency scores of 1, 2, 3, and 4 had median percent dry matter of 20.9, 16.3, 9.6, and 5.8, respectively. Using percent dry matter assessed by fecal consistency scoring were significantly different from each other (P < 0.001). A higher fecal consistency score also was associated with a greater number of Cryptosporidium oocysts shed (P < 0 .0001). Scores of 1, 2, 3, and 4 had median oocyst counts of 0, 0, 1.3 × 10⁶, and 2.8 × 10⁶, respectively. These results suggest that observational scoring is a useful proxy to assess diarrhea in dairy calves.

Effect of nitazoxanide on cryptosporidiosis in experimentally infected neonatal dairy calves

Cryptosporidium is a zoonotic protozoan that is most often diagnosed in association with diarrhea in 1- to 3-wk-old dairy calves. There are neither consistently effective nor approved antimicrobial drugs for treatment in animals. The objective of this study was to test nitazoxanide (NTZ) as a treatment for cryptosporidiosis in experimentally infected dairy calves. A randomized, controlled, and blinded trial was performed using Holstein bull calves obtained from a large commercial dairy. All births were attended by study personnel and calves were fed 4 L of heat-treated colostrum within 1 h of birth. Calves were randomly assigned to treatment or placebo group and maintained for a 32-feeding (16 d) study period. Twenty-three calves were enrolled with 3 lost to follow up. Thirteen calves were assigned to the treatment group and 7 calves to the placebo group. All calves were inoculated with 1 x 10(6) viable Cryptosporidium parvum oocysts at feeding 3. Treatment was a commercially available NTZ product and the placebo was the carrier of the same product. Nitazoxanide was administered at 1.5 g twice per day for 5 d. Nitazoxanide or placebo treatment began after feeding 10 and when the fecal score was greater than 1 out of 3. Outcome measurements included twice-daily fecal and health scores and a once-daily oocyst count by an immunofluorescent antibody assay. Data were analyzed by nonparametric and time-to-event methods. Measures of passive transfer of antibodies, initial body weight, and onset of oocyst shedding were not different between treatment and control calves. Eighty-five percent of the NTZ-treated calves stopped shedding oocysts by the end of the observation period whereas only 15% of the placebo group stopped shedding. The median number of feedings with a fecal score equal to 3 was 2 in the NTZ group while it was 6 in the placebo group. Calves receiving NTZ were 0.13 times as likely to have severe and sustained diarrhea than control calves (95% confidence interval, 0.02-0.98). Treating calves with NTZ reduced the duration of oocyst shedding and improved fecal consistency.

A comparison of the protein constituents of the major body compartments of the dog roundworm, Toxocara canis

An analysis of the protein profiles of intact worms and isolated tissues of adult male and female Toxocara canis worms was conducted. Soluble proteins recovered from homogenized whole specimens and dissected tissues (body wall, reproductive tract, esophagus and intestine) of T. canis adults from several different canine hosts were separated by size using gradient sodium dodecyl sulfate electrophoresis (SDS-PAGE) and visualized with silver staining. SDS-PAGE profiles of worms from different hosts were found to be virtually identical irrespective of sex or tissue type. Recovered proteins ranged in size from 3.4 to 325 kDa. As expected, variations existed between the protein profiles of different body tissues, with only slight variations between the sexes. The largest number of recovered proteins was present in the female reproductive tract extracts.