Further studies on an intermediate host murine model showing that a primary Echinococcus granulosus infection is protective against subsequent oncospheral challenge.
We describe the use of a murine model to evaluate resistance against subsequent challenge following a primary infection with oncospheres of Echinococcus granulosus. Mice (Kunming strain) were infected with hatched oncospheres of Echinococcus granulosus; 21 days later a second challenge was given by a different route of infection. A primary infection by intraperitoneal (i.p.) injection stimulated 100 and 90.5% protection in terms of reduced cyst numbers against a secondary infection given subcutaneously (s.c.) or intravenously (i.v.), respectively. A primary infection given s.c. followed by i.p. or i.v. challenge resulted in 84.0 and 100% protection, respectively. Intravenous infection followed by i.p. or s.c. challenge resulted in 98.5 and 69.4% protection, respectively. With the i.v. route of infection, almost all resultant cysts were present in the lungs. The data show that a primary infection with oncospheres can induce total or a high degree of protection against a subsequent challenge and confirms that natural (concomitant) immunity can be stimulated in the intermediate host as the result of a primary infection. This may explain the decline in hydatid infection in sheep older than 2 years in hyper-endemic areas such as those found in Xingjiang, China. These older sheep may have been earlier infected and have subsequently self-cured, with the primary infection stimulating an immune response that protects the intermediate host animals from further infection.
Zhang
W
W
Molecular Parasitology Unit, The Queensland Institute of Medical Research, 300 Herston Road, P.O. Royal Brisbane Hospital, Brisbane, Qld 4029, Australia.
You
H
H
Zhang
Z
Z
Turson
G
G
Hasyet
A
A
McManus
D P
DP
D000818:Animals; D004285:Dogs; D004443:Echinococcosis / Q000276:immunology*; D004446:Echinococcus / Q000276:immunology*; D005260:Female; D007113:Immunity, Innate / Q000276:immunology; D008168:Lung / Q000276:immunology / Q000469:parasitology; D008297:Male; D051379:Mice; D010270:Parasite Egg Count