Camel calf diarrhea with emphasis on rotavirus infection

Abstract

The role of rotavirus in camel calf diarrhea in four different areas (River Nile, Gedarif, Sennar and Blue Nile and Kordofan States) in Sudan was studied. Data about the epidemiology of camel calf diarrhea its treatment regimen adopted by the owners was collected and analyzed. The detection of rotavirus antibodies using ELISA and antigen using five different techniques was applied. Characterization and isolation in tissue culture of rotavirus from fecal samples was adopted. A total of 383 camel herds were investigated about the incidence of camel calf diarrhea during wet and dry seasons over the three years period of study (2000-2002) in the different four areas focused. The overall morbidity rate of camel calf diarrhea in the four areas of study was 83% while mortality and case fatality rates were 39.9% and 43.3%, respectively. The morbidity, mortality and case fatality rates of camel calf diarrhea were found to be almost the same in the four areas focused during wet and dry seasons with slight increase during wet season. With regards to different treatment regimens adopted to diarrheic camel calves by the owners, 38.2% were left without treatment, 56.9% had received tetracycline while other drugs (Diaclean, sulpha, pamizole, traditional drugs, penicillin, antibiotic plus glucose and flagyle) constituted a very minor percentages. A serological survey was conducted using group A rotavirus antibody detection ELISA on 530 camel sera. The overall percentage of positive samples was 48.1%. Seropositivity was detected in all areas o f study with slightly higher percentage in Sennar and Blue Nile States. The overall percentage of high antibody titer (4+) was 31.4% and 3+ was 22%. Most of the seropositive samples were at 18-36 month of age and adult camels with slightly higher percentage in males than females (56.5% males and 43.5% females). A correlation was found between the seropositivity and the clinical status of diarrhea. The highest percentage of seropositivity was found in healthy camel calves (69.7%). A total of 332 fecal samples were examined for group A rotavirus antigen using ELISA and some of the samples had been examined also by latex agglutination (LA), immunochromatographic test (IC), polyacrylamide gel electrophoresis (PAGE), electron microscopy (EM) and ELISA for group C rotavirus antigen. Rotavirus antigen was detected in 22.6% of samples. Group A rotavirus was detected in 20.2% (13.9% using ELISA and 6.3% using IC test) while group C rotavirus was detected in 2.4%. Group A and C rotavirus were detected in all areas of study. No coronavirus antigen was detected in 302 fecal samples tested. A comparison was made between the different techniques used for rotavirus antigen detection. Out of 46 ELISA positive samples, 17 positive, 12 doubtful, 9 negative and 8 were not tested by IC while 8 positive, 1 doubtful, 17 negative 20 were not tested by LA, 11 positive 34 negative and 1 not tested by PAGE. Six positive, 16 negative and 24 were not tested by EM. Out of 281 ELISA negative samples, 20 IC and 1 LA positive results were obtained. The result revealed a higher sensitivity of ELISA and IC over the other tests. All PAGE positive samples showed the characteristic group A rotavirus short electropherotype. Group A rotavirus VP6 subgroup specificity was detected in 31 out of 42 tested samples in which subgroup II was predominated (54.8%). Reverse transcription polymerase chain reaction (RT/PCR) was applied on 10 ELISA positive samples for detection of group A rotavirus RNA as well as VP4 and VP7 genotyping. Seven samples were positive using RT/PCR from which 5 could be genotyped for VP4 and VP7 genes. Two samples were G11, 2 G3 and 1 was G6 while 4 samples were P[11] and 1 was P[4]. Trials for rotavirus isolation in tissue culture were applied on 29 samples (17 group A, 8 group C and 4 group A and C ELISA positive samples). A progressive rotavirus characteristic cytopathic effect (CPE) was seen on 26 of tested samples (15 group A, 8 group C and 3 group A and C). CPE detected for both groups (A and C) were round cells, granulated, vacuolated, elongated refractile and giant cells. Rotavirus was identified in tissue culture harvest using ELISA and IC for group A and EM for both group A and C rotaviruses. This is the first report for the detection of camel group A rotavirus antigen in different areas of Sudan, the detection of group C rotavirus antigen in camels, the detection of group A rotavirus VP6 subgroup specificity. The results of this study revealed also the first report of camel group A rotavirus genotyping and isolation of group A and C rotavirus in tissue culture.