Survival of nonsporulated Toxoplasma gondii oocysts under refrigerator conditions.

Toxoplasma gondii oocysts are excreted nonsporulated in the feces of the cats into the environment. These oocysts must undergo sporulation to become infectious. Little is known about the factors that influence sporulation of T. gondii oocysts. The present study examined the survival of nonsporulated oocysts under refrigerated conditions over 11-week observation period. Microscopic examination of oocysts indicated that no visible development occurred under refrigerator conditions. The nonsporulated oocysts retained their ability to sporulate when placed at room temperature. The numbers of visually viable appearing oocysts decreased over time. Some oocysts in all samples were infectious for mice despite being refrigerated for up to an 11 weeks before undergoing sporulation. Results indicate that nonsporulated oocysts can survive in the environment for at least 3 months and retain their ability to become infectious when placed under appropriate conditions.     

Larvicidal effects of several chemicals on Strongyloides infective larvae

The larvicidal effects of 11 anthelmintics, 7 pesticides and 4 disinfectants were evaluated with infective larvae of Strongyloides papillosus (SPL) and Strongyloides venezuelensis (SVZ). The lethal concentrations against SPL and SVZ were found to be similar. Three chemicals (dichlorvos, levamisole and trichlorfon) showed highest larvicidal effects. The 50% lethal concentration (LC(50)) values for the three compounds against SPL larvae were 0.08, 0.24, and 0.59 ppm, respectively.     

几种检测弓形虫血清抗体方法的比较分析

本文对5种弓形虫血清IgG抗体检测方法进行比较评价。5种方法平行检测了80份血清,比较各检测方法的阳性检出率,敏感性,特异性,符合率及Youden指数。结果经配对2检验,ELISA-200,IHA,MAT,SPA-ELISA 4种方法在阳性检出率、平行检测结果之间无显著性差异(P<0.05)。ELISA-200敏感性、特异性和符合率均高于90%,Youden指数(0.85)显著高于其他方法(P<0.05)。IHA,MAT,SPA-ELISA 3种方法各指标处于中等水平,各有适合的检测环境。ELISA-100与其他四种方法在检测结果上差异极显著(P<0.01),特异性(38.3%)、符合率(58.75%)及Youden指数(0.383)都显著低于其他方法。     

Lesions in goats fed Toxoplasma gondii oocysts

Tissues of 20 2-3-month-old kids and 17 2-4-year old does fed Toxoplasma gondii oocysts were examined histologically. Kids were necropsied between 3 and 50 days post-inoculation (DPI) and does were necropsied between 10 and 422 DPI. Lesions were seen in tissues of all young goats fed 1000-100,000 oocysts and consisted of acute enteritis, necrosis of mesenteric lymph nodes and encephalomyelitis. Lesions were not seen in does fed 10-10,000 oocysts.     

Incidence of Toxoplasma gondii oocysts in cat feces

Within two years and a half, the faeces of 620 cats coming from Brno and the area around the city were subjected to parasitological examination with special regard to the occurrence of the oocysts of Toxoplasma gondii. Sucrose solution at the specific weight of 1,150 was used as flotation medium. Oocysts of Toxoplasma gondii were eliminated by eight cats (1.29%) at the age from 16 days to 1.5 years. Six of the eight cats were younger than seven months. The Toxoplasma gondii oocysts were eliminated by the cats for 1-16 days while exhibiting signs of short-term scours and swelling of lymph nodes. In all cases the oocysts of Toxoplasma gondii were produced in the summer and autumn seasons (June-December). During the patent period, other coccidia (Isospora felis and Isospora rivolta) were also present in the cats.     

Titration of Toxoplasma gondii oocysts in non-pregnant sheep and the effects of subsequent challenge during pregnancy

Fifty-nine ewes, seronegative to Toxoplasma gondii, were allocated to four groups which received 2000, 200, 20 or no M1 strain toxoplasma oocysts 56 days before mating. Fifty-one of them subsequently became pregnant and were challenged with 10,000 oocysts between 78 and 83 days of gestation. Infection with 2000 oocysts induced a pyrexia, seroconversion and protective immunity in all the recipient animals. Ewes that received either 20 or no oocysts before pregnancy were susceptible to subsequent challenge and severe fetal mortality occurred. In this study 200 oocysts was the threshold value for the induction of toxoplasma infection in sheep, although not all the ewes that seroconverted to this dose were protected against further challenge.     

Examination of cats for the elimination of Toxoplasma gondii oocysts]

Two hundred and two samples of excrements were investigated for the presence of Toxoplasma gondii oocysts. Fifty-two samples were taken from dead domestic cats and a hundred and fifty samples were obtained from wild cats living in various localities of the CSSR. The investigation was orientative and a flotation method with the Breza flotation solution of the specific weight of 1.300 was used. If the finding was positive, residues of the excrements were floated with a saccharose, solution of the specific weight of 1.150 and containing 0.8% of phenol. The oocysts were rinsed several times, then they were sporulated in Petri dishes with water with a 2.5% solution of potassium dichromate. The sporulated oocysts, after rinsing, were injected i. p. to mice. The excrements of the fifty-two domestic cats were negative. Out of a hundred and fifty samples of the excrements of wild cats, one sample with the oocysts of isospore type was found; a biological test with mice proved the oocysts of Toxoplasma gondii. It may be inferred from the results obtained that the elimination of oocysts by cats is the same as given in foreign literature, and the occurrence rate will be about 2%.     

Persistence of encysted Toxoplasma gondii in tissues of pigs fed oocysts

Ten pigs were fed 100 to 10,000 Toxoplasma gondii oocysts. Two pigs died 7 and 11 days later, and 8 pigs were euthanatized at days 38, 38, 91, 126, 168, 169, 170, and 171. From the euthanatized pigs, portions of 15 organs digested in pepsin-HCl solution were inoculated into mice, as a bioassay for viable T gondii. Such organisms were isolated from the brain and heart of these 8 pigs, from the tongue of 7, from thigh muscles of 5, from the diaphragm of 4, from kidneys, liver, and small intestines of 2, and from salivary glands and eyes of 1 pig; but not from lungs, spleen, spinal cord, mesenteric and prescapular lymph nodes of any pig. Results indicate that T gondii can persist in edible tissues of living pigs for at least 171 days and that heart and brain may be the most suitable porcine tissues for epizootiologic surveys.     

The effect of heating against Cryptosporidium oocysts

The effect of heat treatment was examined against oocysts of Cryptosporidium parvum, Cryptosporidium muris and chicken Cryptosporidium sp. isolated in Japan. The oocysts of these species were exposed at 50, 55, 60 and 70 degrees C for 5, 15, 30 and 60 sec in water bath, respectively. To determine the infectivity of heated oocysts, the nice and chickens were inoculated with the treated oocysts and the oocyst output in the feces after inoculation was examined. In C. parvum and chicken Cryptosporidium sp., the oocysts were not detected from mice or chickens which were received oocysts heated at 55 degrees C for 30 sec, 60 degrees C for 15 sec and 70 degrees C for 5 sec. In C. muris, the oocysts were not detected from mice which were received oocysts heated at 55 degrees C for 15 sec, 60 degrees C for 15 sec and 70 degrees C for 5 sec. Consequently, it was clarified that the infectivity of Cryptosporidium oocysts to mice and chickens was lost by heating at 55 degrees C for 30 sec, 60 degrees C for 15 sec and 70 degrees C for 5 sec.     

Soil contamination of Toxoplasma gondii oocysts in pig farms in central China

Toxoplasmosis in pigs is a large threat to pig industry as well as pork consumers. Most pigs become infected by ingestion of oocysts from contaminated environment (soil, water and feed) or infected animal tissues postnatally. In the present study, field studies were conducted to evaluate the relationship between soil contamination status of Toxoplasma gondii oocysts and T. gondii infection in pigs in 12 pig farms with different density of cats in central China. The presence of T. gondii oocysts in soil were determined by PCR and loop-mediated isothermal amplification (LAMP). T. gondii DNA was found in 11 farms with different cat density excepting one farm exposed to low cat density. Twenty (21.1%) and 36 (37.9%) of 95 soil samples were T. gondii positive by PCR and LAMP, respectively (0.01相似文献   

Acute primary toxoplasmic hepatitis in an adult cat shedding Toxoplasma gondii oocysts

A 3-year-old 4-kg neutered male domestic shorthair cat died within 5 days after onset of fever and respiratory distress. At necropsy, all tissues were icteric, and the liver had a diffuse reticular pattern. Histologically, hepatitis and encephalitis were associated with Toxoplasma gondii tachyzoites. Toxoplasma gondii female gamonts and oocysts were found in epithelial cells of intact villi and in epithelial cells desquamated into the lumen. Finding of acute hepatitis and T gondii oocysts in an adult cat without detectable immunodeficiency is unusual, because adult cats rarely have clinical signs of toxoplasmosis during the oocyst-shedding phase.     

Correlation of tissue infection and serologic findings in pigs fed Toxoplasma gondii oocysts

Each of thirteen 6-week-old pigs was inoculated per os with 10,000 sporulated oocysts of Toxoplasma gondii. By postinoculation day (PID) 13, pigs were seropositive by the indirect fluorescent antibody test. Beginning on PID 13 and every 7 days thereafter through PID 97, 1 pig was killed and 6 tissues were examined for T gondii. Of the 13 pigs, 11 were infected, including the 1st pig killed on PID 13, although none of the pigs had gross lesions of toxoplasmosis. Tissues harboring T gondii most frequently were the heart and brain; organisms were detected less frequently in the longissimus muscles, diaphragm, and liver. Toxoplasma gondii was not detected in the bronchial lymph nodes. There was good correlation between antibody and presence of T gondii in these pigs. One additional pig, maintained as a noninfected control, remained seronegative and had no evidence of infection when killed on PID 97.     

Prevention of Toxoplasma gondii abortion in goats by vaccination with oocysts of Hammondia hammondi

Nineteen does (female goats) were dosed with 500,000 oocytes of Hammondia hammondi prior to breeding. At about 90 days of gestation these, and 18 uninoculated does were challenged with 25,000 Toxoplasma gondii oocysts. The 19 H. hammondi--inoculated does produced 26 live and one dead kid (newborn goat). The 18 does not given H. hammondi produced 12 live and 19 dead kids. However, examination of all of the kids by isolation of T. gondii in mice, serology and histology revealed that they were all infected with T. gondii. Thus, while H. hammondi "vaccination" is protective against the deleterious effects of T. gondii on pregnant does, perhaps by reducing the severity of placental lesions, it does not prevent foetal infection.     

Effects of ozone and ultraviolet radiation treatments on the infectivity of Toxoplasma gondii oocysts

Clinical toxoplasmosis in humans has been epidemiologically linked to the consumption of drinking water contaminated by Toxoplasma gondii oocysts. We evaluated killing of T. gondii oocysts after ultraviolet (UV) or ozone treatments by bioassay in mice and/or cell culture. A 4-log inactivation of the oocyst/sporozoite infectivity was obtained for UV fluences >20 mJ cm(-2). In contrast, oocysts were not inactivated by ozone with an exposure (Ct) up to 9.4 mg min l (-1) in water at 20 degrees C. In conclusion, UV treatment can be an effective disinfection method to inactivate T. gondii oocysts in drinking water, but ozone did not show promise in this research.     

Gel-Bead Delivery of Eimeria oocysts protects chickens against coccidiosis

Vaccines composed of either virulent or attenuated Eimeria spp. oocysts have been developed as an alternative to medication of feed with ionophore drugs or synthetic chemicals. The purpose of this study was to evaluate the use of gel-beads containing a mixture of Eimeria acervulina, Eimeria maxima, and Eimeria tenella oocysts as a vaccine against coccidiosis. Newly hatched chicks (Gallus gallus domesticus) were either sprayed with an aqueous suspension of Eimeria oocysts or were allowed to ingest feed containing Eimeria oocysts-incorporated gel-beads. Control day-old chicks were given an equivalent number of Eimeria oocysts (10(4) total) by oral gavage. After 3 days, chicks were randomly assigned to individual cages, and feces were collected between days 5 and 8 postinfection. All samples were processed for total Eimeria oocysts. At 4 wk of age, all chickens and a control nonimmunized group received a high-dose E acervulina, E maxima, and E. tenella challenge infection. Oocyst excretion by chicks fed gel-beads or inoculated by oral gavage was 10- to 100-fold greater than that of chicks spray-vaccinated with the Eimeria oocysts mixture (log 6.3-6.6 vs. log 4.8). Subsequent protection against challenge as measured by weight gain and feed conversion efficiency was significantly greater (P < 0.05) in gel-bead and oral gavage groups compared with spray-vaccinated or nonimmunized groups. Also, gel-bead and oral gavage groups showed no significant difference (P > 0.05) in weight gain and feed conversion efficiency compared with nonchallenged controls. These findings indicate that incorporation of Eimeria spp. oocysts in gel-beads may represent an effective way to deliver live oocyst vaccines to day-old chicks for preventing subsequent outbreaks of coccidiosis in the field.     

Detection of Toxoplasma gondii-like oocysts in cat feces and estimates of the environmental oocyst burden

OBJECTIVE: To estimate the analytic sensitivity of microscopic detection of Toxoplasma gondii oocysts and the environmental loading of T gondii oocysts on the basis of prevalence of shedding by owned and unowned cats. DESIGN: Cross-sectional survey. SAMPLE POPULATION: 326 fecal samples from cats. PROCEDURES: Fecal samples were collected from cat shelters, veterinary clinics, cat-owning households, and outdoor locations and tested via ZnSO(4) fecal flotation. RESULTS: Only 3 (0.9%) samples of feces from 326 cats in the Morro Bay area of California contained T gondii-like oocysts. On the basis of the estimated tonnage of cat feces deposited outdoors in this area, the annual burden in the environment was estimated to be 94 to 4,671 oocysts/m(2) (9 to 434 oocysts/ft(2)). CONCLUSIONS AND CLINICAL RELEVANCE: Despite the low prevalence and short duration of T gondii oocyst shedding by cats detected in the present and former surveys, the sheer numbers of oocysts shed by cats during initial infection could lead to substantial environmental contamination. Veterinarians may wish to make cat owners aware of the potential threats to human and wildlife health posed by cats permitted to defecate outdoors.     

Antitumor activity of Toxoplasma lysate antigen against methylcholanthrene-induced tumor-bearing rats.

Growth of the tumor autoinduced by 20-methylcholanthrene (MC) in rats was inhibited after administration of Toxoplasma lysate antigen (TLA). The antitumor activity of TLA was most obvious in the early stage of tumoral growth. When TLA was administered to rats before the appearance of tumour, tumor formation was delayed slightly. Histopathological studies revealed dense growths of spindle tumor cells in untreated control rat, while enlarged central necrosis with the infiltration of lymphocytes and neutrophils was apparent in TLA-treated rats. According to the immunohistological examination of tumor tissue with anti-Thy-1 antibody, the rats treated with TLA showed large Thy-1 positive granular cells, whereas the untreated rats indicated only a few small Thy-1 positive cells. These observations indicate that TLA is a useful modifier of biological responses to MC-induced tumors.     

Comparison of different commercial DNA extraction kits to detect Toxoplasma gondii oocysts in cat faeces

The cat is the definitive host of Toxoplasma gondii and plays an important role in the transmission of this and other coccidian parasites, e.g. Hammondia hammondi, a protozoon closely related and morphologically similar to T. gondii. A number of techniques to detect T. gondii nucleic acids in feline faeces are described and several extraction kits for isolating pathogen DNA from faeces or soil are commercially available. To compare the performance of such kits with regard to isolating oocyst DNA, a feline sample that had tested negative for coccidian parasites including T. gondii and H. hammondi was spiked with 10(4), 10(3), 10(2), 50 and 10 H. hammondi oocysts. Several ready-to-use stool or soil kits and an in-house method were then used to extract parasite DNA from these spiked faecal samples. Of six kits tested, two were found suitable for the detection of H. hammondi oocysts DNA by the polymerase chain reaction (PCR) in faecal samples with a detection limit of 250 oocysts per 1 g of faecal sample. These two kits revealed a similar, even slightly lower detection limit (50 oocysts per 1 g of sample) when tested with faecal samples spiked with T gondii oocysts.     

Serologic response of red-legged partridges (Alectoris rufa) after oral inoculation with Toxoplasma gondii oocysts

Thirty 5-month-old red-legged partridges (Alectoris rufa) reared in battery were divided into five groups: 4 birds in group A, 14 birds in group B, 4 birds in group C, 4 birds in group D and 4 birds in group E, and were inoculated orally with 10, 50, 10(2), 10(3) and 10(4) oocysts of the OV-51/95 strain of Toxoplasma gondii, respectively. During the experiment, blood samples from all birds were drawn every 3-7 days and at necropsy. Serologic response was measured by the modified agglutination test (MAT) and the latex agglutination test (LAT). One bird from each group was killed at 44, 58, 65 and 72 days after inoculation (DAI). From 72 DAI to the end of the experiment, surviving partridges from group B were killed at weekly intervals. The last partridges were sacrified 100 DAI. MAT was the most sensitive and specific test for detecting T. gondii antibodies in the birds. First positive titers were detected by MAT in all sera on 7 DAI, but titers by LAT did not appear until 13 DAI. Antibody titers detected by MAT on 7 DAI were higher in the partridges with the largest inocula (10(3) or 10(4) oocysts) than those inoculated with 10, 50 or 10(2) oocysts. All surviving birds developed a serologic response to T. gondii, with maximum titers of 512-32,768 in the MAT on 13-17 DAI, and positive titers persisted at least until 100 DAI. To the contrary, LAT reveals only very low antibody titers even in partridges inoculated with the highest dose of T. gondii.