Description of the Infectious Agent and its Incubation Period

Published: 2019-05-28 02:17:19
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Dientamoeba fragilis, the parasite, is a protozoan that resides in the colon of the people and as such, it produces trophozoites. Di means that the trophozoites have two nuclei at the feeding stage of the organism. Ent, on the other hand, refers to enteric surrounding in which the parasite is found. The name of the species fragile means that indeed the stages of the trophozoite are fragile and hence there incubation period is very short. After leaving the human body host in the stool, the parasite does survive long. The cysts may survive for some days to weeks when outside the host but the trophozoites usually degenerate quickly hence making it too hard for identification. The ideal conditions for the identification of D. fragilis need the preparations that are permanently stained of fixed or freshly passed and unpreserved specimens of the stool (Blostein, 1991). The period of incubation varies depending on the serotype, varying from 12 hours to one week but in most cases, it takes 24 to 72 hours.

According to the researcher, Shigellosis is a disease that is infectious, and it is caused by Shigella, which is a bacteria family that usually cause diarrhea in people. The individuals who have the germ bacteria shed it in their feces and thus the bacteria can spread from an infected individual to contaminate food, water or another person directly. The investigator identifies several potential sources of infection in this study. Those source that the researcher suspects to be the likely ones comprise of the specific activities of recreation, the use of facilities such as the restroom as well as the consumptions of food, water for drinking and beverage. However, apart from these sources listed by the investigator, other sources may include a contact with the infected person, the contamination of vegetables in the field or the shipment of the contaminated produce. For instance, simultaneous Shigella outbreaks occurred in October in the year 1983 at two university campuses in Texas, and these schools were 60 miles apart. Between the two campuses, there were common handlers of food, swimming areas, water sources or recreational activities to illustrate the appearance of Shigella at the two campuses. However, the salads that were tossed were found to be in connection with the illness at the two campuses (Medrano, Salinas, Barroso & Reininger, 2010). The investigation portrayed that both had received the shipments of produce from the same organization during the week before the outbreaks. The Shigella found at these two schools were found to be identical when they were analyzed. It was the first report o outbreaks that are related that happen as a result of the contamination of the source of the food and not by the handler of the food as it has always been. As such, the investigator of the study did not remember to mention such as the source of Shigellosis. The simultaneous foodborne outbreaks can trigger a look for potential contamination at each step from handling of the food from the farm up to the kitchen.

Apart from the case-control study design, the investigator could as well use the quasi-experimental study design to evaluate and assess the infectious disease to determine the possible sources. The quasi-experimental design is ubiquitous in the literature of infectious disease, specifically in the areas of the interventions that target the identification of potential sources of the bacteria. There is no much information regarding the limitations and the benefits of this design though but the design can be very useful to sounder study and the causal links that are convincing between the interventions of the infectious disease Shigellosis and the outcomes.

In the research, the Shigellosis disease in particular, the quasi-experimental research design, which at some moments is known as the pre-post-intervention design, can be applied to assess the sources of the infection and its specific interventions. The quasi-experimental design entails a comprehensive range of the intervention studies that are not randomized (Niyogi, 2007). Such studies can be useful where it is not logistically feasible or unethical to carry out a randomized, and the controlled trial of the causal research. The procedure of quasi-experiment design in the case of Shigellosis may be as follows; if the hospital introduces the use of the disinfectant that is alcohol-based, it will seek to investigate the impact of the intervention on the outcome of Shigella resistant bacteria, on the basis of culture of surveillance. To determine the sources, the hospital can measure the rates of acquisition, the place, as well as the time of acquisition once the intervention is implemented. The measurement can be done both before and after the intervention and then analyze the results.


Despite being inexpensive, the case-control used by the researcher presents some problems. First, the study is observational in nature and hence it does not offer the same evidence level like the controlled trials that are randomized. Secondly, the outcomes are likely to be confounded by other factors to the degree of proving a negative response. More so, using this design makes it hard to develop the timeline of exposure to the Shigellosis outcome in the setting of case-control study than within a cohort study design that is prospective (Phalipon, Mulard & Sansonetti, 2008). To correct these issues, the research can opt to use randomized controlled trials or alternative, the prospective cohort study design can be used.

Recommended Measures against Shigellosis

For quite some time, the Organization for World Health. WHO has been attempting to find the vaccine of Shigella, nothing has proved successful yet. For me, therefore, I will advise the public to do the following to prevent the infectious agent.



BLOSTEIN, J. (1991). Shigellosis from Swimming in a Park Pond in Michigan. Public Health Rep., 106, 317-322.

Medrano, B., Salinas, J., Barroso, C., & Reininger, B. (2010). Shigellosis in Hidalgo County, Texas 2005--2009.

Niyogi, S. (2007). Increasing antimicrobial resistancea an emerging problem in the treatment of shigellosis. Clinical Microbiology And Infection, 13(12), 1141-1143.

Phalipon, A., Mulard, L., & Sansonetti, P. (2008). Vaccination against the shigellosis: is it the path that is too difficult or is it the difficult that is the path?. Microbes And Infection, 10(9), 1057-1062



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