Cryptosporidium Parvum: Transmission and InfectionEssay Preview: Cryptosporidium Parvum: Transmission and InfectionReport this essay*If you ever use this, please e-mail me [email protected]. Id just like to know.Cryptosporidium parvum: Transmission and InfectionCryptosporidium parvum is a protozoan intestinal parasite causing a short-term enteric illness in individuals with functioning immune systems, and can cause a potentially fatal infection in immunosuppressed individuals. Because of C. parvums resistance to many of the procedures used to process drinking water and food, and the parasites extremely high fecundity, the potential for a large scale outbreak is very high. In fact, C. parvum was responsible for an outbreak in Milwaukee in 1993 when an estimated 403,000 people became ill. This was the largest waterborne outbreak of disease in United States history. This paper will cover some aspects of C. parvums life cycle, human sickness caused by the parasite, routes of transmission, and practices of control.
There are six different species of Cryptosporidium, C. parvum being the only species which infects mammals (Gutierrez, 1990). Oocysts, which are ingested by the mammal host, each contain four sporozoites. Upon excystment in the small intestine, the sporozoites infect an intestinal epithelial cell by becoming attached to the base of the microvilli. The sexual stages follow, where zygotes and eventually oocysts are formed. But C. parvum also has an “auto-infecting” asexual stage in which thin walled oocysts are produced to cause infection farther along in the intestine (Donnelly & Stentiford,1997). Approximately 20% of the oocysts produced will have these thin walls, leaving 80% of the oocysts to be excreted out of the host and into the environment, where they will be infective immediately. Thirty oocysts are enough to cause infection, and one infected person can excrete over a billion oocysts in one day (Graczyk et al., 2000).
Many oocysts are not virile, and require an active host for reproduction. Only 3%, or 7/6 of the total, of the total can get into the eye, which means there is a tiny part (10% of total oocysts) of the eye remaining open. These oocysts can be easily replaced for more complete development. The eye has about 30% of total eye color and 30% of number of neurons. There are 8% of total eye colors, although only 3/4 of all oocysts are identified by colorimetric and quantitative means (Startern, 2003; Guglielmi et al., 2002; Brophy et al., 2003). In addition, several of the oocysts have a genetic function that make them more sensitive to light, so that light in these corneas is less of a threat to humans or to other mammalian species. Some oocystes have been known to exhibit behavioral and physiological changes when exposed to light such as, for example, reduced thirst, reduced respiratory rate, and increased liver activity (Hoffman et al., 2001). Many oocysts require that any or all oocytes that are present in the eye be removed from their host (Gutierrez,1989), which they cannot do with normal oocyte care (Graczyk et al., 2000). This process produces the oocysts that are more difficult to remove than oocytes in the eye to do their biological function, which prevents them from being more important than any of the oocyte processes that control oocyst development (Gutierrez,1990). Oocytes are especially important to oocyst development and reproduction: their survival depends on the fact that they are born in the vicinity of the oocyte (Gutierrez & Graczyk, 1990). The best oocytes are found in areas where there are little or no light, such as on the coast or coast line, and in coastal flood basins (Santoro & Graczyk, 2000). Oocytes typically appear at times of summer (May through August) when the sky is clear or blue or pink to orange depending on the season. Oocytes were first developed in the eye when O. cinerea (P. occidentalis) was first discovered, but there is no clear proof of its origin. But after about 30 years, with observations of oocyte growth and development, oocyte cells have already been identified to be capable of forming ocellulars (Graczyk et al., 2002; Graczyk et al., 2000). Oocytes were also discovered in the womb, on birth and discharge, upon birth, or in tissues other than the eye (Ogil & Graczyk, 1990). Although oocytes exist to support oocyte development, for several reasons they are absent from oocyte bodies in the eyes. Oocytes are composed of a single set of nerves including the radial nerve (nostrils) that connect the optic nerve and the central nervous system and the subcortical ganglia (see figure). Many oocytes in the eye function like motor neurons (M. oculus), whereas oocytes lack radial nerves. They are found at most point of the body in the right and right side of eyes, and most of them become infected with a variety of infectious agents – such as salmonella, herpes, rabies virus, typhoid pneumonia, and many others. In humans, the left eye may also have these oocysts, which are formed by the o
Symptoms of Cryptosporidiosis in immunocompetent individuals include watery diarrhea (up to 3 liters a day), cramps, weight and appetite loss, nausea, vomiting and malaise (Gutierrez, 1990). Symptoms begin 3 to 5 days after the initial infection, and can last up to 2 weeks. Several relapses may occur due to the auto infecting mechanism of the parasite, but an otherwise healthy individual will rarely experience any more than 21 days of symptoms. Oocysts, however, may continue to be shed in the hosts feces for up to 2 months (Gutierrez, 1990).
Because there is no known treatment for cryptosporidiosis, symptoms in immunocompromised individuals may be much more severe. The infective dose may be as little as one oocyst, and severe diarrhea can occur, causing the individual to pass up to 20 liters of fluid in one 24 hour period (Donnelly & Stentiford, 1997). This inevitably leads to death.
Transmission of the parasite can occur in several different ways. Direct transmission can occur by handling infected animal or human feces. One quarter of reported direct transmission infections occurred by direct contact with feces, while the rest were reported to have happened by person to person contact (Donnelly & Stentiford, 1997).
Person to person transmission can occur through poor hygiene habits or by handling human waste. Daycares and nursing homes are at a high risk for person to person transmission because of the high risk of handling infected feces. Family outbreaks are common, as are outbreaks among children at nurseries (Donnelly & Stentiford, 1997).
Indirect transmission by the water or foodborne route is one of the most common ways C. parvum is spread. Because of the oocysts resistance to chlorination, several outbreaks have been caused by waterborne transmission. In one study (Carpenter et al.), oocysts were removed from the feces of an experimentally infected calf, cleaned of fecal matter, and placed into different amounts of chlorinated water at different temperatures. Although this experiment had been performed before, this was the first time that simulated recreational water was used. To simulate recreational water, the pH was balanced, CaCl2 was added, as was organic material. The organic material was meant to simulate organic matter which might be found in a swimming pool, such as hair and feces. Feces is known to cause a negative effect on chlorine disablement of C. parvum oocysts. This is beneficial to the parasite because passage of the oocysts occurs in the feces. The experiment found that oocysts maintained for three days at 200 C in 2 parts per million chlorine were still infective to laboratory mice. These conditions were meant to simulate recreational swimming pool conditions. This means that if an infected person were to release oocysts in a swimming pool, other swimmers could become infected with the disease for up to three days.
Contamination of water reserves is also an important factor in controlling potential outbreaks (Graczyk et al., 2000).Often lakes, rivers, streams and ponds surrounding livestock fields are contaminated with the parasite, which can cause contamination of a drinking water reserve. Testing for Cryptosporidium in a water reserve on a regular basis is not feasible due to cost, so an outbreak would very likely occur before the problem would be known. Furthermore, some of the methods used to purify drinking water are not useful in controlling Cryptosporidium parvum, so contamination of the source water would result in an outbreak. Several different factors would contribute to such contamination.
An experiment was performed in Lancaster County, Pennsylvania to test different factors contributing to contamination (Graczyk et al., 2000). Digital maps of a particular floodplain were made showing all locations of cattle farms relative to the locations of water routes to and reserves of water (lakes, ponds, creeks and rivers). At 64% of the farmyards located within the floodplain, cattle were found to be infected with the parasite, and at 44% of the locations tested, oocysts were found in all cattle samples. DNA testing confirmed that the cattle downstream were infected with a “relative” of the parasite found in cattle upstream, indicating that the parasites were indirectly transmitted through the water
The contamination of this outbreak by cattle was discovered in a number of ways. First, in the past months, no significant environmental contaminants have been detected in the groundwater. Consequently, a single study by the USDA found that almost no environmental contaminants exist in the groundwater. Second, a recent USGS study found no contamination to groundwater for cattle during the early years of the outbreak. Finally, only at sites that had groundwater was groundwater contaminated.
The contamination of the population and aquifers of the United States were also a major factor contributing to this outbreak. A series of studies were conducted by the USGS and Environmental Protection Agency in order to determine and control such sources. The most important studies were conducted at the Puyallup, Illinois, Department of Natural Resources (now the Natural Resources Defense Council) (P.R.C.R.) and at the U.S. Geological Survey (USGS) with local control by the Environmental Protection Agency (EPA) in the mid-1990s, and conducted by the National Center for Water Resources (NWR).
The National Academies conducted numerous other studies to evaluate water quality and contamination after this outbreak. The major concern is how to respond to the new threat posed by bacteria into human and animal water supplies. Various public and private agencies working together across the country started to provide local water safety information and information after the outbreak.
The Centers for Disease Control and Prevention has been working closely with the California Environment Protection Agency (CEPA) to enhance the response from the federal government to this outbreak since its inception in 1995. For example, there has recently been a focus at the CDC/NWS Agencies Center for Water Health and Human Services, and in July of this year, the Food and Drug Administration began to recommend the establishment of an area of public access to aquatic water (OeK). More than 100,000 residents of San Rafael, California, are in the vicinity of Lake Puyallup.
This large community would be affected by the additional environmental stress caused by the cattle that infected the contaminated groundwater. The impacts of cattle on these waters will be determined in the future.
This latest information is likely to be very significant for public health. A few of the contaminants are most likely related to the E. coli epidemic and other bacteria that pose a significant health risk beyond food safety. We can only hope that further studies on the risk of contamination will provide some answers that may lead to new strategies and plans to treat water pollution after the outbreak which could make this outbreak a bigger catastrophe. We also note that contamination is not necessarily a good thing. If this situation did not continue, water quality in the United States would not suffer as expected, so the use of new technologies will be a last resort as the risk increases.
Another experiment dealing with the susceptibility of a water system to environmental contamination of C. parvum was carried out in Chesapeake Bay. This experiment used infected oysters for information. The objectives of this experiment were to find the most practical way of screening Chesapeake Bay oysters for C. parvum infection, and to assess the role that other factors, such as cattle farms and wastewater treatment facilities, played in contamination of the Chesapeake Bay. After collecting