• Parasites, Hosts and Diseases
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• v.37 no.1
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• pp.33-37
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• 1999

An age-dependent aspect of resistance to Cryptosporidium muris (strain MCR) infection was monitored in Syrian golden hamsters. Mesocricetus auratus. at 1-, 5- and 10-week of age and in ICR mice, Mus musculus, at 3-, 12-, and 15-week of age orally inoculated with a single dose of $2{\times}10^6$ oocysts. respectively. The prepatent periods for both animals were similar, independent of age, but the patency was significantly longer in younger hamsters (P<0.001) and a long tendency in younger mice. Hamsters infected at 1-week of age excreted about 10 times higher oocysts than those at 5- and 10-week of age. However, the total oocyst output was similar among mice of different ages. There was a good correlation between the length of the patency and the total oocyst output in hamsters (R=0.9646), but not in mice (R=0.456l). The immunogenicity of the parasite to homologous challenge infections was very strong in hamsters and relatively strong in mice. These results indicate that acquired resistance to C. muris infection is age-related and the innate resistance is independent of age of hamsters, and that both innate and acquired resistance, on the contrary, are irrespective of age of mice.

• Parasites, Hosts and Diseases
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• v.29 no.2
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• pp.149-160
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• 1991

Each of SPF mice(Scl: ICR strain, 3-week-old males) was inoculated with 5$\times$104 oocysts of Cryptosporidium by stomach tube. The oocysts were large type one which was previously isolated from Korean mice, and passaged in 3-week-old SPF mice. The patterns of oocyst discharge were monitored daily, and in order to observe the ultrastructure of developmental stages the stomach of the mice was examined by transmission electron microscopy (TEM) at 4 weeks post-inoculation. The prepatent period for 6 mice was 5.6 days post-inoculation on the average, and the patent period was 63.2 days. The number of oocysts discharged per day from the mice reached peak on day 36.6 post-inoculation on the average. A large number of oocysts were found in fecal samples obtained from inoculated mice on days 30~50 post-inoculation. C. tsuris was larger than C. parvum at almost every developmental stages, the sixte difference being 1.4 times in oocysts, 2.4 times in sporozoites, 1.6 times in merozoites, and 1.5 times in microgametes. The ultrastructural features of the attachment site of C. tsuris to the mucus cells were remarkably different from those of C. parvum and its closely related species. The anterior projection of the protozoa (C. muris), the outer aspect of which was surrounded by a thick filamentous process of the host cell, has not been reported at any developmental stages of C. parvum or its closely related species. The size of the oocysts of strain RN 66 was larger than that of Korean mice origin. The above results reveal that the large type Cryptosporidium of Korean mice origin is identified as Cryptosporidium muris and this type was named as C. muris (strain MCR).

• Parasites, Hosts and Diseases
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• v.34 no.2
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• pp.155-157
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• 1996

We have successfully maintained Cyptospori, diam mons by cryopreservation. Oocysts were suspended in distilled water, stored at $-20^{\circ}C$ for 24 hrs, and then cryopreserved at $-70^{\circ}C$. Cryopreserved specimens were slowly thawed at $5^{\circ}C$. Oocysts, which had been cryopreserved for 1% months without cryoprotective agents. retained their infectivity by the mouse titration method. Oocysts stored at $5^{\circ}C$ in 2.5% potassium dichromate failed to retain their infectivity beyond 6.5 months.

• Parasites, Hosts and Diseases
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• v.33 no.4
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• pp.377-382
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• 1995

Three-week-old ICR SPF mice were orally inoculated with one of 5 doses ranging from $2{\;}\times{\;}10^2{\;}to{\;}2{\;}\times{\;}10^6$ oocysts of Crwptosporidium tsuris (strain MCR) per mouse. Oocyst inoculation was directly proportional to the amount of oocysts shed and was inversely proportional to the period required for peals oocyst production and to the prepatent period. Peak oocyst production occurred between fifteen and thirty-one days with a patent period from 61 to 64 days. Three days after all mice stopped shedding oocysts, they were orally challenged with a single dose of $2{\;}\times{\;}10^6$ oocysts or the same species. Marked seroconversion for IgG antibody accompanied recovery from mice inoculated with $5{\;}\times{\;}10^5$ oocysts. Mice administered with carrageenan excreted a small number of oocysts for 49.0 days on the average after challenge inoculation (ACI) and control mice for 14.2 days in a dose-independent fashion. Just before challenge infection, phagocytic activity of peritoneal macrophages ($M{\phi}$) and the number of peripheral $M{\phi}$ were dramatically decreased. Mild challenge infection implies that the immunogenicity of C. nuris (strain MCR) is very strong, despite $M{\phi}$ blocker carrageenan administration.

• Parasites, Hosts and Diseases
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• v.35 no.4
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• pp.245-250
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• 1997

The responses of gastric mucosal mast cells (GMMCS) to infection with coccid- ian protozoa, Clptosporinium muris, in mice were examined during primary and challenge infections. Each of three-week-old ICR SPF mice was orally inoculated with a single dose of 2 × 106 oocysts of C. muffs (strain MCR). After oocyst shedding ceased, the mice were orally challenged with a single dose of 2×106 oocysts of the same species. GMMCS reached a peak on days 20-30 postinoculation (Pl) in number, and decreased thereafter. An increase on days 20-30 post-challenge-infection (PCI) was also observed. The mice showed, on the whole, normal profiles of oocyst shedding in droppings. The number of the cells of uninfected control mice remained constant. .Tudging from the above results, it is suggested that mastocytosis correlate with expulsion of C. mans in primary infection and the defense mechanism of challenge infection.

• Parasites, Hosts and Diseases
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• v.36 no.3
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• pp.171-182
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• 1998

A total of nine Korean native kids and two Corriedale lambs, 1-20 days old, were each inoculated per os with a single dose of 2 × 107 oocysts of Cwptospori,mum muris (strain MCR) originated from mice to elucidate the kinetics and developmental stages of the coccidium in small ruminants. Irrespective of host's age, the prepatent period for both animals ranged from 19 to 35 days (28.1 days, on the average) and the patent period 16-85 days (47.8 days), and the total oocyst outputs showed enormous differences. Infection with greater numbers of oocyst outputs was not ordinarily established by transmission experiments. Oocysts discharged from the kids retained their infectivity by the mouse titration method. The immunogenicity of the coccidium and oocyst reproduction were proven by challenge infection and administration of prednisolone acetate. respectively. All the developmental stages of the coccidium in parasitophorous vacuoles were found by transmission electron microscopy in the pits of the gastric glands of a kid inoculated with oocysts and then necropsied on day 44 postinoculation. It indicated the full course of the host-parasite relationship in kids and lambs as well as mice.