Cysts In Water Research Articles

Sedimentation of free and attached Cryptosporidium oocysts and Giardia cysts in water.

Experimental analysis of the sedimentation velocity of Cryptosporidium parvum oocysts and Giardia lamblia cysts was compared with mathematical description of their sedimentation velocities by using measurements of (oo)cyst size and density and the density and viscosity of the sedimentation medium to determine if the sedimentation kinetics of freely suspended oocysts of C. parvum and cysts of G. lamblia can be described by Stokes' law. The theoretically calculated sedimentation kinetics showed a good agreement with the experimentally observed kinetics. Both showed a decline in sedimentation velocity over time, caused primarily by variation in (oo)cyst density. The initial apparent sedimentation velocities in Hanks balanced salt solution at 23 degrees C was 0.35 micron . s-1 for oocysts and 1.4 micron . s-1 for cysts. (Oo)cysts that enter the surface water environment by discharges of biologically treated sewage may be attached to sewage particles, and this will affect their sedimentation kinetics. Therefore, (oo)cysts were mixed with settled secondary effluent. (Oo)cysts readily attached to the (biological) particles in effluent; 30% of both cysts and oocysts attached during the first minutes of mixing, and this fraction increased to approximately 75% after 24 h. The sedimentation velocity of (oo)cysts attached to secondary effluent particles increased with particle size and was (already in the smallest size fraction [1 to 40 micron]) determined by the sedimentation kinetics of the effluent particles. The observed sedimentation velocities of freely suspended (oo)cysts are probably too low to cause significant sedimentation in surface water or reservoirs. However, since a significant proportion of both cysts and oocysts attached readily to organic biological particles in secondary effluent, sedimentation of attached (oo)cysts after discharge into surface water will probably be a significant factor in the environmental ecology of C. parvum and G. lamblia. Attachment to particles influences not only sedimentation of (oo)cysts in surface water but also their behavior in drinking water treatment processes.

Effects of temperature and length of exposure on the mortality of the carrot cyst nematode, Heterodera carotae

A hatchability level of 72% of eggs in Heterodera carotae cysts was notsignificantly affected by keeping the cysts in water at up to 40 C for 2 h, but percentage hatch was strongly reduced by keeping the cysts for 2 h in water at 47.5, 50 and 52.5 C. Keeping soil with cysts of H. carotae with a hatchability before treatment of 27% at temperatures between 32.5 and 45 C for 2 and 4 h did not affect percentage hatch of the eggs in these cysts but longer exposures increased it in two ways and decreased it in one way. This resulted in a positive correlation between percentage hatch and length of exposure up to a smaller maximum hatch the higher the temperature. At still longer exposures percentage hatch was negatively correlated with length of exposure. Whether the decrease is due to mortality of the eggs or, partly, to reversible inactivation remains to be investigated. In contrast to hatching tests with root diffusate, probably almost all eggs will hatch in the field under a host crop. Therefore, only the adverse effect of the heat treatments on hatching is ofpracticalimportance for the estimation of the effect of solarization. To separate it from the effects that increased percentage hatch in the tests, a model was made of the interaction of the separate effects. It was based on linear relationships between log duration of exposure to different temperatures and probit relative increase and decrease of hatching rates, and linear relationships between treatment temperature and log length of exposure required to obtain a given effect of one of the two increasing effects and of the decreasing effect of the treatments. The coefficient of variation of hatchabilities that were affected by the increasing but not by the decreasing effect of the treatments, relative to those predicted by the model, was 7.1% against 7.8% after treatments that had no effect on percentage hatch, whereas the relationship between log length of exposure and probit percent reduction of hatchability by the treatments was linear. The relationship between probit hatchability ( h ) due to the decreasing affect of the treatments and temperature ( T ) during t hours is probit h = a b log t dTr - T in which T is a reference temperature. For T - 10 T r r T = 45 C, a = 11.047, b = 1.44 and d = 0.637 for H. carotae . A good r T r approximation of this relationship is log h= k l t dTr - T with k = 2.453, - T T r l = 0.03735 and d = 0.637. These relationships probably also apply, with T r other parameter values, to other nematode species. To calculate the effect of fluctuating temperatures t dTr - T is replaced in the equations by T Sigma (t dTr - T). T

The status of UK methods for the detection of cryptosporidium spp oocysts and giardia spp cysts in water concentrates

Current UK methods for the isolation and enumeration of Cryptosporidium spp oocysts and Giardia spp cysts in water concentrates are time-consuming and inefficient, providing minimal information regarding the biology of the organism. Minimising the portion of sample concentrate examined can reduce the level of confidence in the result obtained and this issue requires appreciation by the water regulators. Alternative methods for isolation and enumeration require corroboration with the established method using a variety of water types. Developments that increase information regarding the biology of these organisms should be encouraged. Not only does method performance (recovery efficiency, reproducibility etc), but also method significance (integrity of health, operational and regulatory assessments etc) require to be addressed. For Cryptosporidium the fluorogenic viability assay can not only assist in the decisions taken by health officials when oocysts are found in water supplies but also in designing catchment assessment and sampling policies for individual treatment plants, yet few laboratories are experienced in this assay.

The status of UK methods for the detection of Cryptosporidium spp oocysts and Giardia spp cysts in water concentrates

Current UK methods for the isolation and enumeration of Cryptosporidium spp oocysts and Giardia spp cysts in water concentrates are time-consuming and inefficient, providing minimal information regarding the biology of the organism. Minimising the portion of sample concentrate examined can reduce the level of confidence in the result obtained and this issue requires appreciation by the water regulators. Alternative methods for isolation and enumeration require corroboration with the established method using a variety of water types. Developments that increase information regarding the biology of these organisms should be encouraged. Not only does method performance (recovery efficiency, reproducibility etc), but also method significance (integrity of health, operational and regulatory assessments etc) require to be addressed. For Cryprosporidium the fluorogenic viability assay can not only assist in the decisions taken by health officials when oocysts are found in water supplies but also in designing catchment assessment and sampling policies for individual treatment plants, yet few laboratories are experienced in this assay.

A comparison of phase contrast microscopy and an immunofluorescence test for the detection of Giardia spp. in faecal specimens from cattle and wild rodents

As part of a study on the presence of Giardia cysts in water, a commercial direct immunofluorescence (DIF) test for the cysts was evaluated and compared to phase contrast microscopy. Forty faecal samples were collected from cattle; 31 contained Giardia. All 31 samples were positive by DIF whereas only 17 were detected by microscopy. The detected Giardia cysts were identified as belonging to the G. duodenalis group. 216 faecal samples were collected from wild rodents ( Apodemus flavicollis, A. sylvaticus and Clethrionomys glareolus); 103 contained Giardia. Cysts were detected in 97 samples by DIF and in 57 by microscopy; 51 samples were positive by both methods. Nineteen rodents harboured cysts which morphologically resembled G. duodenalis. Specific identification was possible only by phase contrast microscopy, but the results suggested that DIF was superior for the detection of Giardia cysts in faeces of the animals tested.

ConcentratingGiardiacysts in water by tangential flow filtration compared with centrifugation

Abstract Centrifugation, tangential filtration, and sedimentation were compared as methods of concentrating cyst‐containing wash water from filters. A range of cyst concentrations were used on duplicate samples. The cysts were concentrated by one of the above methods and the detectable number of cysts noted. The ability of the methods to process samples with sediment and the overall time taken to process a sample was assessed. The method of choice for the concentration of Giardia cysts in water is centrifugation.

Microbiological Characteristics of Point‐of‐Use Precoat Carbon Filters

Experiments conducted with commercial point‐of‐use precoat carbon filters showed that these filters can significantly and consistently reduce the heterotrophic plate count (HPC), coliforms, enteric viruses, and protozoan cysts in water. Although the effect of silver in the precoat filters on HPC organisms was inconclusive, the presence of silver dramatically reduced coliform levels. The antimicrobial effect of copper in these filters was similar to, but much less than, that of silver.

ISOLATION AND DETECTION OF GIARDIA CYSTS FROM WATER USING DIRECT IMMUNOFLUORESCENCE1

ABSTRACT: A water‐sampling apparatus used for the isolation and detection of Giardia cysts in water has been designed and tested. The sampling apparatus uses one of a variety of pumps or waterline pressure to move water through a filter. Two of the optional pumps are lightweight enough to make the apparatus portable and thus suitable for sampling in remote areas. This technique of sample processing produces good cyst recovery in much less time than is required with previously established methods. Giardia cysts are identified using direct immunofluorescence.

Evaluation of a tangential-flow multiple-filter technique for detection of Giardia lamblia cysts in water.

A system of tangential-flow filtration was evaluated for use in the detection of Giardia cysts in drinking water. This method was more sensitive in recovering cysts than a frequently used wound-orlon system of through-filtration.

Changes in the adenine nucleotide content of cysts of Globodera rostochiensis associated with the hatching of juveniles

SUMMARYThe content of AMP, ADP and ATP within single cysts of Globodera rostochiensis (60–80 fig dry weight) was determined as ATP to an accuracy of ± 10‐11 mol by a bioluminescent technique, after microenzymic methods had been used to phosphorylate AMP and ADP to ATP.Results for a total of 120 cysts showed that a change occurs in the adenylate energy charge of their contents after they have been exposed to potato root diffusate. Cysts in water had a mean adenylate energy charge of 0–63 (s.E. ± 0–04), but a randomly selected group of cysts after 24 h treatment with potato root diffusate had a significantly lower mean of 0–49±0–04. In a second, similar experiment, cysts in diffusate for only 8 h had an energy charge of 0*55 ± 0–03, but this value was not significantly less than the corresponding mean of o‐6i ±0–03 of cysts that remained in water.The results indicate an effect on the metabolism of the unhatched juveniles that occurs too soon after the addition of diffusate to be directly due to any increase in locomotor activity. Apparently, the primary action of the hatching factor had affected many juveniles within 24 h of the addition of potato root diffusate to the cyst.

Occurrence of a Nematode Worm in a City Water Supply

DURING the development of a procedure in May 1955 for the detection of Endameba histolytica cysts in water (i) by the membrane filter technique, concentrates of treated Ohio River tap water were found to contain motile nematode larvae of microscopic size. Exa inations of tap water collected at different parts of the city * revealed that these larvae were present in the entire distribution system. The examination was continued for 4 months and the larvae were persistently found, mostly alive, at densities of 1-20 per gallon, except on one occasion when as many as 100 larvae per gallon were detected. It is of particular interest that these nematode larvae as well as the experimental ameba cysts remained viable for at least 100 min in a hypochlorite solution containing 1.8-2.4 ppm free residual chlorine at a pH of 8.3-8.4

Investigations on the Emergence of Larvae from the Cysts of the Potato-root Eelworm, Heterodera rostochiensis.

The foregoing results throw light on the conditions under which hatching tests can be carried out. In the first place, pre-soaking cysts in water for a period of 10 days increases the rate of larval emergence but has no effect on the total number of hatchable larvae. Increase in temperature has a similar effect up to 25°C, but at 80°C. hatching is virtually inhibited. Volume of diffusate per cyst is without effect either on the number of hatchable larvae or on their rate of hatching. Neither was any effect observed from alterations in pH between 8.2 and 8.1. The effect of dilution is more or less linear when dilution is plotted geometrically against cither the number of hatchable larvae or the latter expressed as a proportion of the original cyst contents and subjected to angular transformation. For the effect to be appreciable, dilution must be of a high order. Dilution to a half or a quarter of the original concentration has little appreciable effect. The effect of dilution on the rate of hatching is not obvious and the variations in it resulting from dilution are probably random. Direct sunlight inhibits hatching, diffused daylight is without effect as compared with darkness ; cysts exposed to the action of sunlight and diffusate do not hatch when later removed to the dark. It appears reasonable to assume that this may be due to some lethal effect.