Transmission food ingestion

HAV infection primarily occurs through transmission by the fecal-oral route, person-to-person, or by ingestion of contaminated food or water. The incidence of HAV correlates directly with low socioeconomic status, poor sanitary conditions, and overcrowding. Rates of HAV infection have increased among international travelers, injection drug users, and men who have sex with men. 

Campylobacter species are thought to be a major cause of diarrhea. Transmission of infection occurs primarily by ingestion of contaminated food or water. 

Fig. 6.6 Cysts are resistant forms and are responsible for transmission of giardiasis. Both cysts and trophozoites can be found in the faeces (diagnostic stages) (1). The cysts are hardy, and can survive several months in cold water. Infection occurs by the ingestion of cysts in contaminated water, food or by the faecal-oral route (hands or fomites) (2). In the small intestine, excystation releases trophozoites (each cyst produces two trophozoites) (3). Trophozoites multiply by longitudinal binary fission, remaining in the lumen of the proximal small bowel where they can be free or attached to the mucosa by a ventral sucking disc (4). Encystation occurs as the parasites transit toward the colon. The cyst is the stage found most commonly in non-diarrhoeal faeces (5). Because the cysts are infectious when passed in the stool or shortly afterwards, person-to-person transmission is possible. While animals are infected with Giardia, their importance as a reservoir is unclear.

Children are most hkely to experience illness with Y. enterocolitica infection. Transmission of infection occurs frequently by ingestion of contaminated food or water. The organisms have been isolated from a variety of food sources, including pigs and raw goat and cow milk. Refrigeration does not deter the development of adherence and invasive virulence factors. 

Giardiasis, caused by Giardia intestinalis, is the most commonly reported intestinal protozoal infection in the U.S. Infection results from ingestion of cysts in fecally contaminated water or food. Human-to-human transmission via the fecal-oral route is especially common among children in day-care centers and nurseries, institutionalized individuals, and male homosexuals. 

Calcium is found in equal proportion in intracellular fluid and extracellular fluid. It is combined with phosphate in bone and with protein (albumin) in the serum. A patient receives calcium from ingesting calcium-containing food. Calcium plays a critical role in transmission of nerve impulses, blood clotting, muscle contraction, and the formation of teeth and bone. There is also growing evidence that calcium can help with weight loss. 

Salmonella paratyphi is a bacterial enteric (intestinal) infection with an abrupt outbreak, which produces the following symptoms continued fever, headache, malaise, enlarged spleen, rose spots on the trunk of the body, and diarrhea. These symptoms are similar to those of typhoid fever, but the death rate is much lower. Mild and asymptomatic infections may also occur upon exposure. Outbreaks and locations are similar to those of the other salmonella bacteria. The infectious dose is 1000 organisms by ingestion. Transmission occurs by direct or indirect contact with feces or, in rare cases, urine of patients or carriers. It is spread by food, especially miUc and dairy products, shellfish, and in some isolated cases, water supplies. Incubation depends on the strength of the dose, but usually 1-3 weeks for enteric fever and 1-10 days for gastroenteritis. Antibiotic treatment with chloramphenicol, ampicillin, or TMP-SMX is usually effective. 

Ingestion of contaminated milk, followed by regurgitation and inspiration of the contaminated food, is a less common mode of transmission. Other modes of transmission to humans, including lick bites and human to human transmission, are rare. 

Human infection with arenaviru.ses is incidental to the natural cycle of the viruses and occurs when an individual comes into contact with the excretions or materials contaminated with the excretions of an infected rodent, such as ingestion of containinaied food, or by direct contact of abraded or broken skin with rodent excrement. Infection can also ixcur by inhalation of tiny particles soiled with rodent urine or saliva (aerosol transmission). The types of incidental contact depend on the habits of both humans and rodents. For example, where the infected rodent species prefers a field habitat, human infection is associated with agricultural work. In areas where the rodent species habitat includes human homes or other buildings, infection occurs in domestic settings. 

Humans become intecied by inhaling infectious aerosolized particles of rodent urine, feces, or saliva, by ingesting food contaminated with virus, by contamination of mucu.s membranes with infected body fluids, or by directly exposing cuts or other open wounds to virus-infected blood. LCMV infection has also been documented among staff handling infected hamsters. Person-to-person transmission has not been reported, with the exception of vertical transmission from an infected mother to fetus. 

Thus the foodstuffs meat and plants contain mineral substances which are necessary for man and animals to survive. However, they can also contain substances of a type which, as alien or noxious substances, may either directly or indirectly cause toxic symptoms. By way of the food chain, these pollutants can be introduced into the human body. The food chain is either very simple or it contains a number of different transmission links. The simplest form of the food chain is the absorption of air through breathing or of water by drinking. More complicated processes are the absorption of harmful substances from the soil via the plant, which in turn is eaten by the animal, whereupon animal products are ingested by man. 

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