Protozoa, single-cell microbes, are the smallest organisms in the animal kingdom. Considered parasites, protozoa survive in the environment for long period of times by feeding off a host body's nutrients. As a result, they frequently cause illness and have been implicated in disease outbreaks that affect public health. Transmission into the body is virtually seamless and begins with dirty hands. But there are other methods protozoa enter the body.
Contaminated Water
Water contaminated with protozoa is particularly problematic. Fecal-based protozoa which cause digestive tract diseases such as giardia and cryptosporidium, are resistant to chlorination, which is a common practice in water treatment. Protozoa also survive on food and surfaces washed with contaminated water; once ingested, they cause illness. This is problematic because they continues to survive at least a week after digestive symptoms abate. According to Cornell University Extension, this hardiness implicates it in future outbreaks. Another more insidious water-borne protozoa, naegleria, thrives in warm freshwater lakes and ponds. It enters the body through the nasal passages and travels to the brain and spinal cord. Once there, it destroys live tissue and can cause encephalitis-type symptoms and even death. Though chlorine does kill aegleria, using it to treat freshwater lakes and ponds kills fish and other wildlife.
Insect Bites
Though malaria is one of the best-known insect-borne protozoa transmitted through the bite of a mosquito, there are other insect species responsible for protozoa transmission into the body. Flies, cockroaches and coprophagic beetles, because of their close proximity to humans, are also responsible for transmitting protozoa to humans. These insect groups feed off of human and animal waste, decomposing flesh and garbage where protozoa live. The insects mechanically carry the protozoa to other surfaces where the protozoa can thrive and be ingested into the body.
Hand to Hand Transmission
Hand-to-hand and hand-to-mouth transmission of protozoa are common ways for protozoa to enter the body. The most common source of protozoa infection is from unsanitary bathroom and poor hand-washing practices, in daycare centers and health-care institutions. Protozoa travel from one person's hand to another, from contaminated food and water, from your baby's diaper pail, kitty litter boxes and even from the saliva or your family dog. Hand-to-hand protozoal infections can be controlled through good hygiene practices such as thorough hand washing and the use of synthetic gloves when contaminated waste is handled.
Pets
Dogs and cats provide unconditional love. They also, unwittingly, spread fecal-based protozoa. The most common mechanism of transmission is through the fecal-hand-mouth method. However, dogs who roll or eat animal feces, can spread the disease if they lick your mouth. Protozoal infections in cat are excreted in the feces. The best prevention against transmission is frequent hand-washing with soap. Dogs should be restricted from foraging freely or eating cat feces which is often a carrier of toxoplasmosis, a protozoa that can cause birth defects or miscarriage in pregnant women.
Sexual Transmission
Trichomonas vaginal is a protozoa that feeds on the natural bacteria lining the vaginal opening and canal. If infected, a woman may experience inflammation, pain and a yellow-green discharge. Men who are infected tend to be asymptomatic. This protozoa can live outside of the body on toilet seats, in bathtubs and on towels. It is transmitted through sexual contact and can reinfect if not treated with an anti fungal treatment. Frequent infections of trichomonas vaginal is can increase the risks of pregnancy complications and a susceptibility to the HIV virus.
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