Microbe: Trichuris Trichiura
Although not microscopic the parasitic worm, Trichuris Trichiura or whipworm, is studied and taught in similar fashion as any other microbe by microbiologist as well as epidemiologist. Compared to other microscopic organisms such as bacteria and viruses the physical differences are immense including unicellularity and general taxonomy but they equally share similar traits of a parasitic life style. The life cycle and pathogenesis of whipworms undergo the same steps as all other invasive microbes. They must first find a viable host, enter the host, survive and reproduce to eventually spread into other hosts to repeat the process and further the reproduction of their species.
Whipworms get their name from the whip-like shape with heads and the thick tails. Their heads only contain an esophagus and the tails contain the reproductive organs and intestines. An adult female whipworm typically has a longer, thinner anterior end and a thicker posterior. Compared to the female, the male is smaller with a physical characteristic of a coiled posterior end. Whipworms can grow to be 3-5 cm long as adults, while the female ends up typically being longer. The eggs they produce are a brownish-yellow color with and oval or even football shape. The only known host of Trichuris Trichiura are humans but there are similar species such as trichuris vulpis that infect canines. Children are especially vulnerable to exposure of the worms eggs because of the fact that they often play in dirt then stick their fingers in their mouth without washing their hands.
The life cycle of Trichuris Trichiura begins when unemrbyonated eggs are deposited into soil. The eggs reach a two cell stage and eventually an advance cleavage stage. The embrynoted eggs finish their life cycle in the human body as full adults. The life cycle is completed when females and males mate to produce offspring at the rate of about 2000–10000 eggs per day. Females are known to produce a pheromone to attract males, when they are ready to mate the male coils around a female with his curved area over the female genital pore, both the male and female have a single gonad. The life cycle from egg all the way to mature adult whipworms takes only a few months. According to the CDC, adult female whipworms can live up to five years.
Trichuris Trichiura infestations can be traced back to the times of prehistoric man; where they have been found in preserved bodies. However, the first written record of whipworm was made in 1740 by an Italian scientist, Morgani, he discovered adult whipworms in the colon of a adult man. In 1761, the morphology was accurately reported by a German physician, Roedere. He provided accurate drawings of the parasite and in the latter part the eighteenth century the organism received its taxonomy classification. They are members of the nematoda phylum and the adenophorea class. An article on the origins and demography of whipworms in humans and pigs found evidence of an origin for Trichuris Trichiura in Africa which was then carried with human ancestors to Asia and into South America. A shift from human host to pigs may have occurred in Asia where Trichuris suis, the species found in pigs, must have been transmitted globally by natural host dispersal and anthropogenic factors.
Infection mechanisms
Infection of the parasite Trichuris Trichiura happens unexpectedly and by accident, it is more likely to be common in less developed countries where food cannot always be properly cleaned. Before infection into a new host occurs the female whipworm lays eggs in the large intestine of an already infected human. The eggs leave the body through the feces and must land onto warm moist soil to become embryonated, this can take anywhere from 2-3 weeks. The exact incubation period of whipworms is not one hundred percent positive but immature eggs in soil under favorable conditions take about three weeks to mature. Ten days minimum are needed to mature before ingestion by the human host is ideal. After three weeks the eggs have embryonated which means they are infective and ready to be ingested into the human body. The eggs reach the human digestive tract by means of contaminated unwashed and uncooked vegetables, rice, beans or unwashed hands. After consumption the larvae will hatch in the small intestine, invade and start growing. Whipworms live and develop into adults in both the cecum and ascending colon. The adult worms then use their head to thread into the intestinal wall where they become fixed in that location. If another whipworm, of the opposite sex, passes by the posterior end hangs loosely in the colon ready to mate with them. Once the eggs are produced they leave the body through human waste and the process repeats itself all over again.
Whipworms can be transmitted by different organisms, if an animal is infected with whipworms and its feces end up in the soil of a crop the food may be infected with the eggs of the specific whipworm if it goes unwashed. The World Health Organization states that Trichuris Trichiura is the third most common nematode that infects humans. The infection of whipworm is most prevalent among children, and in North America, infection occurs frequently in immigrants from tropical or sub-tropical regions. An estimated 600-800 million people are infected worldwide with Trichuris Trichiura while 3.2 billion people live at risk because they are in regions where the worm is common.
Symptoms
A small amount of whipworms may not cause any noticeable symptoms but if a person is infected with hundreds of worms, then they might have bloody diarrhea and anemia due to the loss of vitamins and iron. The worms food source include the host tissues, such as blood, this leads to the loss of iron and protein. The whipworms lodge themselves onto the intestinal tract and the colon this in turn leaves open wounds inside the host which can cause inflammation of the intestinal wall. Whipworms have also been known to cause loss of appetite which in turn reduces the amount of nutritional intake and physical fitness of the host. Heavy infections of whipworm can have painful passage of stool that contains a mixture of mucus, water, and blood. In extreme cases one might develop rectal prolapse which means the rectum may come out, if pushed hard enough while relieving oneself. In another extreme case mental retardation can occur, In children the heavy infection may be associated with growth retardation and impaired cognitive development. (CDC 2010)
Epidemiology
Whipworms are an infectious parasite that can be found in almost all parts of the world but that are more frequently found in tropical countries. Tropical weather is ideal for the growth of Trichuris Trichiura eggs because they need a warm moist climate, low light, wet soil, and lots of rain for optimal life development. (Roberts, 2000) Poor sanitation practices only increase the spread of whipworms, they occur more frequently in areas where untreated human feces is used as fertilizer or open defecation occurs. The whipworm infection has a prevalence of 50 to 80 percent in some regions of Asia and also occurs, though not as high, in rural areas of the southeastern United States. Whipworm can be found all over the world, not just tropical environments, some other locations include Europe and North America. A 1987 study conducted by the CDC and state health departments found that 1.2% of 216,275 random stool samples were infected with Trichuris trichiura, this was one of the highest rates of prevalence for any nematode at the time. (CDC 2010)
Treatment
Trichuris Trichiura is diagnosed by examining stool samples and observing if there are any smooth, brown, unembryonated eggs. The World Health Organization recommends two medicines for treating whipworm, they include, albendazole (400 mg) and mebendazole (500 mg) . These drugs are effective and inexpensive treatments for the parasitic whipworm. They are also easy to administer by non-medical personnel. They have been put through extensive safety testing and have been used to help treat millions of people infected with whipworm, only a few and minor side-effects have been recorded.
Prevention
To prevent infection of whipworm one should take care of personal hygiene and food handling. Properly washing and cooking your food can be the easiest way to prevent any kind of infection. Wash, peel, or cook all raw vegetables and fruits before eating, especially those that have been grown in soil that has been fertilized with manure. Freezing food for a few days would kill any parasites present. Obvious prevention measures include avoiding contact with soil that may be contaminated with human feces, even fertilizer that may have human feces for crop nutrients. Washing your hands with soap and hot water before handling any food would further protect against many kinds of microbes. As far as preventing children from catching a whipworm infection, teaching the importance of washing hands to prevent many types of diseases should be a top priority in all parents lives.