Comparison between meat quality of Hanzhong White pigs and carcass weight.

A total of 48 carcasses of crossbred Hanzhong White pigs were divided into 3 groups (I, 90-99 kg; II, 100-109 kg; III, 110-119 kg) to investigate the influence of carcass weight on meat quality. The intramuscular fat content of the 3 groups increased from 1.90 to 4.90%; for meat color, Warner-Bratzler shear force, drip loss, and oxidation-type muscle fiber percentage, and muscle fiber diameter of the longissimus lumborum, the indices in group II and group III were better than those in group I (P < 0.05). The saturated fatty acid and polyunsaturated fatty acid percentages of the longissimus lumborum muscle (2.80 and 37.30%, respectively) in group II were significantly lower than those in the other 2 groups, while the monounsaturated fatty acid percentage was the highest (59.10%). In conclusion, our results suggest that a carcass weight of 100-109 kg is sufficient to produce acceptable meat quality of Hanzhong White pigs.

[Longitudinal observation on the control of intestinal helminthiasis].

OBJECTIVE: To search suitable measure for rapid control intestinal helminthiasis and long-term strengthen efficacy. METHODS: The treatment was taken in egg-positive population of intestinal helminthiasis in 1986-1988. The treatment was carried out only in the selected population in 1989-1992. No measure was taken in 1993-2000. RESULTS: (1) The prevalence rate of hookworm, Ascaris and Trichuris decreased to 3.2%, 37.3% and 3.5% respectively after administration of albendazole twice a year for 3 years. (2) The prevalence rate of hookworm continued to decrease to 0.5% after treatment on selected population. (3) The prevalence rate and the intensity of hookworm has been less than 1% and 10/LPG for 8 years. No hookworm larvae had been isolated from the soil. CONCLUSION: The hookworm transmission was effectively controlled in the study site.

The effect of cobalt-60 irradiation on the infectivity of Toxoplasma gondii.

Toxoplasma gondii cysts in the tissues of experimentally infected mice and pigs were irradiated with cobalt-60 at various doses and used to infect mice and kittens. Loss of parasite infectivity was confirmed following irradiation whereas control animals inoculated with non-irradiated infected tissues became infected. Experiments were repeated to calculate the minimal effective dose (MED) of irradiation to eradicate parasite infectivity. The MED for the Chinese NT strain and the American ME-49 and TS-2 strains of T. gondii cysts in mouse and pig tissues was approximately 0.6 kGy. The infectivity for mice of NT strain bradyzoites irradiated at a dose of 0.45 kGy was reduced 10,000-fold. Such irradiation may be valuable in practical operations to control T. gondii in pork products.

[Effect of gamma-irradiation on infectivity of Clonorchis sinensis metacercariae].

The purpose of the present study was to observe the survival and development of Clonorchis sinensis metacercariae in their final hosts after Co-60 gamma irradiation exerting on both metacercariae isolated or in fish. Guinea pigs or albino rats were orally infected by gavage. Bio-assay, fecal examination for ova and dissection of infected animals were used for the estimation of minimum effective dose of gamma irradiation to control infectivity of Clonorchis sinensis metacercariae. Results showed that the minimum effective irradiation dose for isolated metacercariae was 0.05 kGy. The LD50 of the irradiation dose for metacercariae in fish was 0.05 kGy, and the minimum effective dose was 0.15 kGy. No significant difference in radiation susceptibility to Co-60 gamma irradiation was found among Clonorchis sinensis metacercariae in fishes collected at different localities in the northern, middle or southern parts of China. The present finding suggests that irradiation of the fish at a dose of 0.15 kGy could control the infectivity of Clonorchis sinensis metacercariae and thus be adopted as a control measure in preventive medicine.

Effect of cobalt-60 irradiation on the infectivity of Paragonimus westermani metacercariae.

A study was made to observe the effect of cobalt-60 irradiation on the viability of Paragonimus westermani metacercariae in Sinopotamon chekiangense crabs. The crabs were collected in mountain regions of the Zhejiang Province of China in which paragonimiasis is endemic. Adult cats and albino mice were infected with metacercariae irradiated at different doses. Dissection of the host animals was conducted 90 or 30 days, respectively, after infection for recovery of lung flukes. Anti-metacercariae antibody in infected mice was measured by enzyme-linked immunosorbent assay (ELISA). Results showed that metacercariae were unable to grow into adult worms in cats after exposure to gamma irradiation at a dose of 0.10 kGray. However, a small number of metacercariae exposed to a dose of 2.0 kGray excysted and survived in 1 mouse for 30 days. No worm was recovered from mice when the metacercariae were irradiated at a dose of 2.5 kGray. Seropositive results by ELISA were obtained when the mice were infected with metacercariae irradiated at doses ranging from 2.0 to 3.5 kGray.

Studies on the use of cobalt-60 gamma irradiation to control infectivity of Clonorchis sinensis metacercariae.

The purpose of the present study was to observe the survival and development of Clonorchis sinensis metacercariae in their final hosts after Cobalt-60 gamma irradiation of isolated metacercariae or the parasite in fish. Guinea pigs or albino rats were orally infected with irradiated metacercariae by gavage. Bioassay, fecal examination for ova, and necropsy of infected animals, were the methods used for the estimation of minimum effective dose of gamma irradiation to control infectivity of the metacercariae. Results showed that the minimum effective irradiation dose for isolated metacercariae was 0.05 kGy. The LD50 of the irradiation dose for metacercariae in fish was 0.05 kGy, and the minimum effective dose was 0.15 kGy. No significant difference in radiation susceptibility to Co-60 gamma irradiation was found among C. sinensis metacercariae in fishes collected at different localities in northern, middle or southern parts of China. The present finding suggests that irradiation of fish by 0.15 kGy could control infectivity of C. Sinensis metacercariae and thus be adopted as a control measure in preventing infections.

[Serological epidemiologic surveillance on filariasis by ELISA].

In 1984-1990 longitudinal or sectional serological surveillance on filariasis by ELISA with Brugia malayi adult antigen was carried out in 6 villages, Yuhang County, Zhejiang Province, where malayan filariasis had been under control. During that period the microfilaraemia rate of inhabitants had been declining continuously till nil, the positive rate and mean optical density (OD) value in ELISA for positive inhabitants concurrently declined year by year, especially for children under age of 10. By the 5th year after control both the positive rate and mean OD value were close to those of healthy persons living in nonendemic areas of filariasis, no positivity was found in children. In the meantime, ELISA was used to detect serum antibodies in members of a family who were infected with bancroftian filariasis and inhabitants living around them in 1990. Positive rate of ELISA was higher in these inhabitants (8.33%) than in healthy persons (2.53%), and positive ones were detected from children under age of 10. The results suggest that the detection of antifilarial antibody by using ELISA is an effective method for the surveillance of filariasis.

[Clinical observation on efficacy of ivermectin in the treatment of intestinal nematode infections].

A total of 166 cases were divided into 3 groups: group A comprised 55, group B 54 and group C 57 cases. Group A received ivermectin 0.1 mg/kg orally at a single dose, the cure rates were 100%, 3.8% and 50% for ascaris, hookworm and trichuris, infections respectively: group B received ivermectin 0.2 mg/kg orally at a single dose, the corresponding cure rates were 95.5%, 11.8% and 76.5% respectively; group C received pyrantel pamoate 10 mg/kg orally at a single dose, the corresponding cure rates were 95.5%, 29.6% and 31.6% respectively. Although the cure rates were very low for hookworm infection in both group A and B, however, a number of adult worms of Ancylostoma duodenale and Necator americanus were expelled aster medication; It indicates that ivermectin has some effects on these two species of human hookworm. Side effects were mild and transient in all groups.

Studies on the control of hookworm and other soil-transmitted helminthiases in farmers in Zhejiang Province, China.

Different periodic selective chemotherapeutic schemes were used to control hookworm and other soil-transmitted helminthiases in eight villages in five counties in Zhejiang Province, China, 1985-1988. The results showed that the prevalence rates of hookworm, ascariasis, and trichuriasis decreased from 35.0-74.4%, 47.0-.76% and 22.9-47.5% to 3.2-15.8%, 9.9-47.8%, and 3.5-31.2%, respectively, using pyrantel pamoate (10 mg/kg for 1-2 days) or albendazole (400 mg for 1-2 days, once or twice a year for 2-3 years). The eggs per gram of feces of hookworm and Trichuris trichiura also dropped markedly after control. Moreover, the mean hemoglobin levels of sampled populations increased after several treatments. The authors recommend periodic selective chemotherapy as the main method to control soil-transmitted helminthiases, especially hookworm infections.

Studies on the use of cobalt-60 irradiation to control infectivity of Toxoplasma gondii cysts.

Mouse brains harboring the Chinese NT strain of Toxoplasma gondii cysts were homogenized with normal saline and irradiated with cobalt-60 gamma rays at various doses. The homogenate was introduced intraperitoneally into NIH mice or per os into kittens. Loss of infectivity was confirmed according to the following criteria: no cyst found in mouse brain impression smears on the 50th day after inoculation; no oocyst found in feces of kittens 3-15 days after inoculation; subinoculation in mice and a negative IHA test. All bioassays, parasitological examinations and serological tests in the control group gave positive results. Activity of radioactive source: 10 KCi; uniform dosage: 1238 rad/min; dose range of irradiation: 0.1-1.0 KGy. Minimal effective dose of gamma rays to control infectivity of T. gondii cysts was 0.55 KGy. Infectivity of bradyzoites irradiated with gamma rays at a dose of 0.45 KGy decreased by 10,000 times. Minimal effective dose of gamma rays to control infectivity of American ME-49 and Ts-2 strain, is slightly higher (0.6KGy) than that of NT strain. These studies present useful data for practical use of cobalt-60 to control infectivity of T. gondii in meat products.