Molecular and Histopathological detection of Cryptosporidiosis in calves in Chittagong

Abstract

Cryptosporidium is an intestinal protozoan parasite of livestock and human and cause cryptosporidiosis which is also a common disease of cattle especially neonatal calves. Cryptosporidiosis is commonly asymptomatic but sometimes associated with persistent diarrhea in calves. The aim of the present study was to carry out pathological and molecular investigation of cryptosporidium infection in calves. The study was conducted during June, 2015 to January, 2016. During the study period fecal sample were collected from 160 calves with less than 45 days age from a total of 50 dairy and beef farms located in Chittagong Metropolitan Area and Patiya Upazilla of Chittagong when 5 dead calves with a history of diarrheal illness were also examined for gross and histopathological examination. The fecal samples were first screened by modified ZiehlNeelsen (Z-N) staining technique for the detection of cryptosporidium oocysts under light microscope which is characterized by pink to bright red spherical bodies and later confirmed by polymerase chain reaction (PCR) using 18s rRNA gene. Z-N positive fecal samples were used for DNA extraction Cryptosporidium spp. was confirmed by amplifying 18srRNA gene primer. The positive samples yielded 580bp band with the use of 1% agarose gel electrophoresis for PCR amplified products. The overall prevalence of Cryptosporidiosis in crossbred calves was 9.37% (15/160) by Z-N techniques and 1.88% (3/160) by nested PCR amplification which is statistically significant (p<0.05). The prevalence of Cryptosporidium was also significantly higher in diarrhoeic calves (42.85%) than non diarrhoeic (7.9%) calves. During necropsy examination bad odors, bloody mucous membrane with fluid filled watery fecal contents were found in two dead calves. For histopathological examination tissue samples were collected from dead calves and preserved in 10% buffered formalin. After tissue processing and routine H&E staining of intestinal tissue section revealed atrophied villi and sloughing of mucosa with reactive cellular infiltration. It is evident that the prevalence of cryptosporidiosis in bovine calves in these areas is under diagnosed and the clinical status of infection was not potentially high. It can be concluded that Cryptosporidium spp. infection is prevalent in Bangladesh and adult cattle could serve as reservoirs for the zoonotic infection in humans.