Korean J Parasitol.  2009 Jun;47(2):131-138. 10.3347/kjp.2009.47.2.131.

Lambs Infected with UV-Attenuated Sporocysts of Sarcocystis ovicanis Produced Abnormal Sarcocysts and Induced Protective Immunity against a Challenge Infection

Affiliations
  • 1College of Science, King Saud University, P.O. Box 12455, Riyadh 11451, Saudi Arabia. azema1@yahoo.com
  • 2Zoology Department, Faculty of Science, Beni-Sueif University, Egypt.
  • 3College of Medicine and Medical Sciences, Taif University, Taif, Saudi Arabia.

Abstract

The present study surveyed the prevalence of natural infection of the sheep esphagus muscle with sarcocysts of Sarcocystis ovicanis and examined induction of protective immunity using UV-attenuated sporocysts. The overall prevalence of natural infection of the sheep was 95%. Infectivity of the collected sarcocysts was confirmed by shedding of sporulated oocysts after feeding infected esophageal tissues to dogs. To induce protective immunity, lambs were immunized 3 times (once a week) with 1.5 x 10(4) sporocysts exposed to UV-light for 30 min (UV-30 group) or 60 (UV-60 group) min and then challenged with 1.5 x 10(4) normal sporocysts at the 3rd week post the 1st vaccination. These lambs showed high survival and less clinical signs of sarcocystosis than normal infected lambs. The attenuated sporocysts produced abnormal cysts; small in size and detached from the muscle fiber. These abnormalities were more obvious in UV-60 group than UV-30 group. Also, the IFN-gamma level and lymphocyte percentage were increased while the total leukocyte count was decreased in the UV-60 group compared with other groups. The high level of IFN-gamma may be an evidence for the induction of Th1 responses which may have protective effect against a challenge infection.

Keyword

Sarcocystis ovicanis; UV-attenuated sporocysts; protective immunity; IFN-gamma
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