Echinostoma caproni in rats: worm population dynamics and host blood eosinophilia during primary infections with 6, 25 and 50 metacercariae and resistance to secondary and superimposed infections

Abstract

Hooded-Lister rats were inoculated with 6, 25, 50 or 100 metacercariae of the intestinal trematode Echinostoma caproni. Worm establishment and the pattern of egg excretion were followed during the course of primary infections with 6, 25 and 50 metacercariae. Peripheral blood eosinophilia was followed at all infection levels. After 1 month, worm recovery and faecal egg output showed a gradual decline with increasing duration of infection. High worm burdens were expelled later than smaller worm burdens, and egg output persisted longer in animals exhibiting a high initial egg output. The level of blood eosinophilia increased with increasing degree of infection and with the level of egg output. A marked concomitant resistance to superimposed infection was observed on the challenge of rats harbouring 21- and 49-day-old infections with 50 metacercariae. In addition, rats were partially resistant to secondary infection at challenge day 14 following anthelmintic removal of primary 7-day-old infections with 50 metacercariae and were completely resistant at challenge day 7 following elimination of a primary 14-day-old primary infection.

Kinetics of Echinostoma Caproni (Trematoda: Echinostomatidae) Antigens in Feces and Serum of Experimentally Infected Hamsters and Rats

“…Golden hamsters only develop a limited capacity to expel primary infections resulting in chronic infections. In contrast, E. caproni in rats undergoes a gradual worm rejection, and the infection is lost at 49-70 DPI (Hansen et al, 1991;Toledo, Espert, Muñoz-Antoli et al, 2003). Our study compares the course of the infection in both host species by presenting quantitative data on the kinetics of antibodies and coproantigens.…”

“…According to these works, hamsters display a high degree of compatibility, whereas rats exhibit a low level of compatibility (Christensen et al, , 1990Odaibo et al, 1988Odaibo et al, , 1989Hansen et al, 1991;Mahler et al, 1995) using the criterion of worm survival. Golden hamsters only develop a limited capacity to expel primary infections resulting in chronic infections.…”

“…For instance, hamsters and mice show a high level of compatibility with this echinostome species, whereas rats and jirds display a low level of compatibility (Odaibo et al, , 1989Christensen et al, 1990;Hansen et al, 1991;Mahler et al, 1995; Toledo, Espert, Muñoz-Antoli et al, 2003). This classification is based mainly on worm survival observed in each host species.…”

Immunology and pathology of echinostome infections in the definitive host.

“…Increases in the number of blood eosinophils have been observed in rats infected with E. caproni (Hansen et al 1991) , and mice (BALB/c and C3H/HeN strains) infected with E. hortense ) . The degree of blood eosinophilia was closely related with the worm burden in each case.…”

“…For each echinostome species, expulsion of primary infections occurs rapidly in a number of rodent species, while in other species chronic infections are developed . The elimination of E. caproni primary infections in rats occurred at 7-8 weeks postinfection (wpi) (Hansen et al 1991 ;Toledo et al 2004a) , whereas worm survival in hamsters showed a persistence of at least 20 wpi (Toledo et al 2004b) , and in mice the longevity of the adult worms reached 23 wpi (Fried and Peoples 2007) . The elimination of E. trivolvis from mice occurs within 2-3 wpi (Weinstein and Fried 1991) , while in hamsters worms survived for up to 123 days postinfection (dpi) (Mabus et al 1988) .…”