Survival Of Oocysts Research Articles

Survival of Cryptosporidium species in environments relevant to foods and beverages.

To provide data on the survival of Cryptosporidium oocysts in a range of conditions relevant to foods and beverages. Cryptosporidium parvum and C. hominis oocysts were stored in buffered media at different pH values and with various acids. In addition, neutral solutions with high salt (4.5% w/v), glycerol (20% v/v), sucrose (50% w/v) or ethanol (9 and 40% v/v) were used to determine their effects on survival. After storage periods of between 1 h and 14 days, viability was assessed using sporozoite ratio or infection of MRC-5 cell monolayers (not previously reported for culture of this organism). With all treatments, and with both assay techniques, viable oocysts were found at the end of the storage periods. However, treatments with one of the following additions: high salt, glycerol, sucrose or ethanol showed a negative and statistically significant effect on survival. Decline was noted after 1 day or even 1 h of treatment. MRC-5 cells are suitable for infection by C. parvum and C. hominis. Both tissue culture and sporozoite ratio gave broadly similar survival results and the greatest effects were seen with addition of components which reduced water activity. This study has provided useful additional information to the food industry when considering the risk posed by this organism.

Survival of Cryptosporidium parvum Oocysts after Prolonged Exposure to Still Natural Mineral Waters

The survival kinetics of purified Cryptosporidium parvum oocysts of both human and ovine origin, immersed in four still natural mineral waters (total dissolved salts ranging from 91 mg/liter to 430 mg/liter) and reverse osmosis water was assessed by inclusion or exclusion of the fluorogenic vital dyes 4′,6-diamidino-2-phenylindole and propidium iodide over a 12-week period. Semipermeable chambers were used to contain the oocysts while immersed in each mineral water type, permitting both intimate interactions between oocysts and matrices and straightforward sampling for viability assessments. The viability of both oocyst types, assessed at weekly intervals, remained unaltered after 12 weeks at 4°C, whereas a progressive decline in the viability of both oocyst isolates was observed when immersed in mineral waters at 20°C. At 20°C, approximately 30% of oocysts remained viable after 12 weeks incubation. Here, temperature was the major factor that adversely affected oocyst survival, although higher mineral content was also proportionally and significantly associated with this increased oocyst inactivation. The prolonged survival of oocysts at 4°C in our studies indicates that they could survive for prolonged periods of time in U.K. groundwaters (average temperature ~10°C) and thus represent a potential public health hazard if contamination of mineral water sources by viable oocysts were to occur.

Sporulation and Survival of Toxoplasma gondii Oocysts in Seawater

We have been collaborating since 1992 in studies on southern sea otters (Enhydra lutris nereis) as part of a program to define factors, which may be responsible for limiting the growth of the southern sea otter population. We previously demonstrated Toxoplasma gondii in sea otters. We postulated that cat feces containing oocysts could be entering the marine environment through storm run-off or through municipal sewage since cat feces are often disposed down toilets by cat owners. The present study examined the sporulation of T. gondii oocysts in seawater and the survival of sporulated oocysts in seawater. Unsporulated oocysts were placed in 15 ppt artificial seawater, 32 ppt artificial seawater or 2% sulfuric acid (positive control) at 24 C in an incubator. Samples were examined daily for 3 days and development monitored by counting 100 oocysts from each sample. From 75 to 80% of the oocysts were sporulated by 3 days post-inoculation under all treatment conditions. Groups of 2 mice were fed 10,000 oocysts each from each of the 3 treatment groups. All inoculated mice developed toxoplasmosis indicating that oocysts were capable of sporulating in seawater. Survival of sporulated oocysts was examined by placing sporulated T. gondii oocysts in 15 ppt seawater at room temperature 22-24 C (RT) or in a refrigerator kept at 4 C. Mice fed oocysts that had been stored at 4C or RT for 6 months became infected. These results indicate that T. gondii oocysts can sporulate and remain viable in seawater for several months.

Examination of Attachment and Survival of Toxoplasma gondii Oocysts on Raspberries and Blueberries

Examination of Attachment and Survival of Toxoplasma gondii Oocysts on Raspberries and Blueberries

Cryptosporidium parvum oocyst inactivation in three soil types at various temperatures and water potentials

The interaction between soil types, temperature, and soil water potential may have differential effects on the survival of Cryptosporidium parvum oocysts in the terrestrial environment. We examined the effects of three soil types (a silty clay loam, silt loam, and loamy sand), three temperatures (4, 20, and 30 °C), and three soil water potentials (−0.033, −0.5 and −1.5 MPa) on the inactivation kinetics of oocysts. Sentinel chambers were filled with air-dried and sieved soil, brought to the appropriate soil water potential, and inoculated with 2×10 6 freshly purified oocysts. The inoculated chambers were buried in the same bulk soil at the appropriate water potentials and incubated at one of the three temperatures. Triplicate chambers were removed from the bulk soil on days 0, 22, 43, 84 and 156. Sentinel oocysts were extracted, and assayed for potential infectivity by the dye permeability method. Oocysts suspended in sterile distilled water and incubated with the sentinel chambers were used as controls for the effect of temperature. The soil water potentials investigated did not affect oocyst inactivation at any temperature or with any of the three soil types. Rates of oocyst inactivation increased significantly between 4 and 20 °C, but not between 20 and 30 °C with the exception of oocysts incubated in the silty clay loam. Oocyst survival appeared to be significantly greater in the silt loam soil than in the two other soil types when incubated at 20 °C; and at 30 °C oocyst survival was significantly less in the silt clay loam than in the other two soil types. Rates of sentinel oocyst inactivation at all three soil water potentials were significantly lower than the control oocysts in water at the three test temperatures. Thus oocyst survival in soil was not affected by the water potentials between −0.033 and −1.5 MPa; it was affected by soil texture; but temperature appeared to be the factor most affecting oocyst survival. In the critical ambient range of temperature in temperate climates oocysts may survive for months in agricultural soil, and pose a threat to surface waters.

Survival of Cryptosporidium parvum oocysts recovered from experimentally contaminated oysters (Ostrea edulis) and clams (Tapes decussatus).

Samples of two species of shellfish that form part of the human food chain (the oyster Ostrea edulis and the marine clam Tapes decussatus) were experimentally contaminated with Cryptosporidium parvum oocysts. Changes in the viability of oocysts subsequently recovered from the shellfish were evaluated by means of an immunofluorescent antibody technique (IFAT) and inclusion/exclusion of the fluorogenic vital dye propidium iodide. There was a sharp decrease in oocyst viability during the first 4 days, with 15-25% viable oocysts remaining thereafter. In addition the infectivity of these oocysts at 10 and 31 days post-contamination was demonstrated using a suckling murine model.

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.

Long-term survival of Cryptosporidium parvum oocysts in seawater and in experimentally infected mussels ( Mytilus galloprovincialis)

Transmission of infectious oocysts of Cryptosporidium parvum via surface- and drinking-water supplies has been reported and many surface waters flow into the sea, potentially causing runoff of animal-infected faeces. Eating raw mussels is a common practice in many countries, increasing the public's risk of acquiring enteric pathogens. The aims of the present study were to estimate how long C. parvum oocysts remain infectious in artificial seawater, to determine if the oocysts are retained in mussel tissues ( Mytilus galloprovincialis), and how long they maintain their infectivity. Oocysts were incubated in artificial seawater at 6–8°C under moderate oxygenation and the infectivity of oocysts was tested five times, over a 12 month period after incubation in seawater, in BALB/c mice. Each pup was inoculated per os with 10 5 oocysts and killed 5 days p.i. Oocysts remained infectious for 1 year. Forty mussels held in an aquarium containing artificial seawater filtered out more than 4×10 8 oocysts in a 24 h period. Oocysts were detected in the gill washing up to 3 days p.i., in the haemolymph up to 7 days p.i., and in the intestinal tract up to 14 days p.i. Oocysts collected from the gut of mussels 7 and 14 days p.i. were observed to have infected mice. These results suggest that C. parvum oocysts can survive in seawater for at least 1 year and can be filtered out by benthic mussels, retaining their infectivity up to 14 days, so seawater and molluscs are a potential source of C. parvum infection for humans.

Survival of infectious Cryptosporidium parvum oocysts in seawater and eastern oysters (Crassostrea virginica) in the Chesapeake Bay.

Oocysts of Cryptosporidium parvum placed in artificial seawater at salinities of 10, 20, and 30 ppt at 10 degrees C and at 10 ppt at 20 degrees C were infectious after 12 weeks. Those placed in seawater at 20 ppt and 30 ppt at 20 degrees C were infectious for 8 and 4 weeks, respectively. These findings suggested that oocysts could survive in estuarine waters long enough to be removed by filter feeders such as oysters. Thereafter, 30 Eastern oysters, Crassostrea virginica, were collected with a dredge or with hand tongs at each of six sites within Maryland tributaries of the Chesapeake Bay in May and June and in August and September of 1997. Hemocytes and gill washings from all oysters were examined for the presence of Cryptosporidium oocysts and Giardia cysts by immunofluorescence microscopy utilizing a commercially available kit containing fluorescein isothiocyanate-conjugated monoclonal antibodies. Giardia was not detected by this method from any of the 360 oysters examined. Presumptive identification of Cryptosporidium oocysts was made in either hemocytes or gill washings of oysters from all six sites both times that surveys were conducted. In addition, during August and September, for each of the six sites, hemocytes from the 30 oysters were pooled and gill washings from the oysters were pooled. Each pool was delivered by gastric intubation to a litter of neonatal mice to produce a bioassay for oocyst infectivity. Intestinal tissue from two of three mice that received gill washings from oysters collected at a site near a large cattle farm and shoreline homes with septic tanks was positive for developmental stages of C. parvum. These findings demonstrate for the first time that oysters in natural waters harbor infectious C. parvum oocysts and can serve as mechanical vectors of this pathogen.

The survival and transmission of oocysts of Eimeria alabamensis in hay

From a permanent pasture where young cattle had contracted coccidiosis due to Eimeria alabamensis 2 years previously, hay was harvested and fed to six 2–4 month old calves 15 days, 4 months or 8 months after being harvested. the excretion of oocysts by these exposed calves was compared with that by five control calves of similar age which were housed in the same premises but feld hay from a ‘coccidia-free’ field. All calves fed the contaminated hay developed patent E. alabamensis infections and excreted 142000 to 4.2 million oocysts of this species per gram of faeces starting 8 days after the hay was first fed. Five of them had soft (porridge-like to gruel-like) faeces and/or poor appetite. The control calves excreted no or very few oocysts and had firm faeces and unaffected appetite. It is concluded that making hay from pastures contaminated with oocysts of E. alabamensis is unsatisfactory if the hay is to be used for feeding young cattle.

Survival of Oocysts of Eimeria alabamensis on Pastures under Different Climatic Conditions in Sweden

The extent to which oocysts of the coccidian parasite Eimeria alabamensis can survive the winter and cause clinical coccidiosis in different parts of Sweden was investigated. Fecal samples were collected between May and July 1993 from calves on 59 farms where calves had grazed the same pasture for at least 5 consecutive years. The farms were situated in 9 regions of Sweden with different climatic conditions in the winter. On each farm, 5 samples of feces were collected from the floor of the calf-house before the calves were turned out in the spring, and again from the pasture on days 4 or 5, 8 or 9 and 10 or 11 after they were turned out. Overwintering of oocysts of E. alabamensis was considered to have occurred if an increase in the excretion rate of oocysts of this species could be demonstrated 8 to 11 days after calves had been turned out to pastures that had not been grazed since the previous autumn. Oocysts were shown to have overwintered on 27 farms, representing all 9 regions. Samples from 20 (34%) of the farms representing all the climatic regions contained more than 850,000 oocysts per g of feces. This was comparable with the numbers found in animals with clinical coccidiosis due to E. alabamensis. Delaying turnout until the beginning of July did not affect the infection rate of the calves. However, calves which were turned out to pastures that had been grazed by older cattle or horses, either earlier in the spring or in previous years, excreted significantly fewer oocysts than calves which were turned out to pastures that had been grazed only by calves. A questionnaire answered by 321 dairy farmers revealed that of the 298 farmers who turned their first-season grazing cattle out to traditional pastures, 179 (60%) had used the same pasture for at least 5 years. These 179 farmers had experienced a significantly higher incidence of diarrhoea in their calves during the first 2 weeks at pasture than those farmers who had used different pastures.

A low cost, low technology container for studying the survival of transmission stages of parasites and other pathogens in water-related environments

The design of a low cost, low technology container suitable for studying the survival of transmission stages of parasites or other organisms within aquatic or water-related environments is described. The container was tested over a period of 47 days in three environments (mains tap water, river water and cow faeces) in studies on the survival of oocysts of Cryptosporidium parvum. As well as facilitating repeated sampling, the containers prevented bacterial colonisation and allowed oocysts to remain in contact with the soluble matter of the selected environments throughout the study.

Survival of Cryptosporidium parvum oocysts under various environmental pressures.

The survival of various isolates of Cryptosporidium parvum oocysts under a range of environmental pressures including freezing, desiccation, and water treatment processes and in physical environments commonly associated with oocysts such as feces and various water types was monitored. Oocyst viability was assessed by in vitro excystation and by a viability assay based on the exclusion or inclusion of two fluorogenic vital dyes. Although desiccation was found to be lethal, a small proportion of oocysts were able to withstand exposure to temperatures as low as -22 degrees C. The water treatment processes investigated did not affect the survival of oocysts when pH was corrected. However, contact with lime, ferric sulfate, or alum had a significant impact on oocyst survival if the pH was not corrected. Oocysts demonstrated longevity in all water types investigated, including seawater, and when in contact with feces were considered to develop an enhanced impermeability to small molecules which might increase the robustness of the oocysts when exposed to environmental pressures.

Effect of disinfection of drinking water with ozone or chlorine dioxide on survival of Cryptosporidium parvum oocysts.

Demineralized water was seeded with controlled numbers of oocysts of Cryptosporidium parvum purified from fresh calf feces and subjected to different treatments with ozone or chlorine dioxide. The disinfectants were neutralized by sodium thiosulfate, and neonatal mice were inoculated intragastrically and sacrificed 7 days later for enumeration of oocyst production. Preliminary trials indicated that a minimum infection level of 1,000 oocysts (0.1-ml inoculum) per mouse was necessary to induce 100% infection. Treatment of water containing 10(4) oocysts per ml with 1.11 mg of ozone per liter (concentration at time zero [C0]) for 6 min totally eliminated the infectivity of the oocysts for neonatal mice. A level of 2.27 mg of ozone per liter (C0) was necessary to inactivate water containing 5 x 10(5) oocysts per ml within 8 min. Also, 0.4 mg of chlorine dioxide per liter (C0) significantly reduced infectivity within 15 min of contact, although some oocysts remained viable.

Human toxoplasmosis in Somalia. Prevalence of Toxoplasma antibodies in a village in the lower Scebelli region and in Mogadishu

The acquisition of Toxoplasma antibodies in various age groups was studied in 2 populations in Somalia, inhabitants of a village in the southern part of the country and residents in Mogadishu. The overall prevalence of antibodies was 56% in the village and 40% in Mogadishu. In both populations, antibodies were acquired early in life. At the age of 10 years, 44% of the villagers and 31% of the Mogadishu children were seropositive. In Europe and the USA the highest rate of antibody acquisition has been recorded in young adults. This difference may indicate different routes of transmission. In Europe and the USA Toxoplasma is transmitted mainly by the ingestion of undercooked pork or lamb. Undercooked meat is seldom consumed in Somalia, and pork not at all. However, the soil in Somalia is heavily contaminated with cat faeces and the humid climate in the southern part of the country may contribute to long survival of oocysts. In the villages all household activities are performed on the ground and in Mogadishu children play mainly outdoors on the ground. It therefore seems that conditions in Somalia favour transmission by oocysts rather than by infected meat. The early acquisition of antibodies in Somalia suggests that infection during pregnancy and, therefore, congenital toxoplasmosis are rare.

Survival of Coccidia in Poultry Litter and Reservoirs of Infection

The survival of coccidia was studied in poultry litter, dust, soil, and invertebrate animals. The populations of coccidia in litter were recorded during broiler growout in 16 broiler houses and in floor-pen trials involving anticoccidial drugs. The viability of oocysts declined rapidly in poultry litter regardless of the species; it was retained best in 40% moisture at 4 C. Sporocysts from broken oocytes did not survive even short exposure to poultry litter. Survival of oocysts was poorest at temperatures higher than 4 C, regardless of the carrier. In four floor-pen experiments designed to study the efficacy of anticoccidial drugs, the oocyst counts correlated in a general way with lesion scores and performance, indicating the oocyst counts might be useful along with other parameters to judge the effectiveness of drugs. Coccidia were transmitted to susceptible chicks by feeding them darkling beetles, flies, or house dust from poultry houses. More carrier samples were positive during the warmer months. Oocyst counts in litter of commercial poultry houses were very low during the first or last weeks of broiler growout but were high during the normal 3-to-6-week stress period. These results confirm the poor survival of oocysts in poultry litter and suggest that carryover from one flock to the next depends on the survival of a few oocysts in dust or arthropod vectors.

THE SPECİES OF EİMERİA OCCURRİNG İN CATTLE İN TURKEY

ClimaLİc conditions in many parts of Turkeyare suitable for . sporulation and survival of coccidia oocysts. Routine faecal examinations in our laboratory show that cattle discharge a wide variety. of oocysts during all seasons of the year and a hundered percent incidence of infeetiem is frequently encountered in healthy herds. Clinical eoecidiosis is also known to be present in ealves and has been eonsidered important for economie losses. In recent years a survey of oocysts occurring in the faeces of eattle in neighbourhood of Ankara was carried out and eight species of Eimeria were identified (22). The identification was based on the morphological criteria of their unsporulated oocysts alone, but ıecent works (17, 18, ıg, 23, 31) have shown that sporulated oocysts are neeassary for valid differentiations. Indced there is praeticaIIy not enough information on the oceurrenee of the various speeies of Eimeria present in eattIe in this country (35). The purpose of this paper is to set out the results obtained from a survey of faeeal specimens whieh were examined in order to determine the speeie~of Eimeria present in eattle in Turkeyand to provide a brief note on the diagnostic features of ooeysts of these .speeies for the guidanee. of workers interested in. the disease in this country.

THE SPORULATED OOCYSTS OF EIMERIA ANKARENSIS N. SP. AND OF OTHER SPECIES OF EIMERIA OF BUFFALO IN TURKEY AND TRANSMISSION OF FOUR SPECIES OF EIMERIA FROM BUFFALO TO COW CAL VE S

Climatic conditions in many parts of Turkeyare suitable for sporulation and survival of coccidia oocysts. Our investigation shows that cattle pass a wide variety of oocysts in their feces during all seasons of the year and nearly hundred percent incidence of infection is encountered in some healthy heards. Clinical coccidiosis is also known to be common in this animal and it is of considerable economic importance. But the problem in buffalo (Bubalus bubalis) has not received much attention and no work on its coccidia was undertaken (36).