Tuesday, July 27, 2010

Trichinella spiralis

Trichinella spiralis is a nematode parasite, occurring in rats, pigs, and humans, and is responsible for the disease trichinosis. It is sometimes referred to as the "pork worm" due to it being found commonly in pork or rat products that are undercooked.Trichinella species are the smallest nematode parasite of human, which has an unusual life cycle and one of the most widespread and clinically important parasites in the world. The small adult worms mature in the intestine of an intermediate host such as a pig. Each adult female produces batches of live larvae, which bore through the intestinal wall, enter the blood (to feed on it) and lymphatic system, and are carried tostriated muscle Once in the muscle, they encyst, or become enclosed in a capsule. Humans can be infected by eating infected pork or wildcarnivores such as fox, cat or bear.

Trichinella spiralis is a parasitic nematode that has a direct life cycle, meaning that it completes all stages of development in one host. The larval forms of T. spinalis are encapsulated as a small cystic structure within the infected host. Human typically become infected when they eat improperly cooked pork or Trichinella infected meat. When a human eats the infected meat, the larvae are released from the nurse cell (due to stomach pH) and migrate to the intestine where they burrow into the intestinal mucosa, mature, and reproduce . Interestingly, juveniles within nurse cells have an anaerobic or facultative anaerobic metabolism but when they become activated adopt an aerobic metabolism characteristics of the adult.

The first symptoms may appear between 12 hours and two days after ingestion of infected meat. The migration of worms in the intestinal epithelium can cause traumatic damage to the host tissue and the waste products they excrete can provoke an immunological reaction. The resulting inflammation can cause symptoms such as nausea, vomiting, sweating and diarrhea. Five to seven days after the appearance of symptoms facial edema and fever may occur. After 10 days intense muscular pain, difficulty breathing, weakening of pulse and blood pressure, heart damage and various nervous disorders may occur, eventually leading to death due to heart failure, respiratory complications or kidney malfunction.

Muscle biopsy is used for trichinosis detection. Several immunodiagnostic tests are also available. Typically patients are treated with either Mebendazole or Albendazole but efficacy of such products are uncertain. Symptoms can be relieved by use of analgesics and corticosteroids.

Wednesday, July 21, 2010

Naegleria fowleri

Naegleria fowleri is a "brain eating" amaeba, free-living excavate form of protist typically found in warm bodies of fresh water, such as ponds, lakes, rivers, and hot springs. It is also found in soil, near warm water discharges of industrial plants, and minimally chlorinated swimming pools, (there is no evidence of this amoeba living in ocean water) in an amoeboid or temporary flagellate stage.


Naegleria fowleri exists in nature in three forms: a flagellate, an ameboid and a cyst.

Flagellate stage: A biflagellate form occurring when trophozites are exposed to a change in ionic concentration such as placement in distilled water. The transformation of trophozoites to flagellate form occurs within a few minutes.

Trophozoite stage: The reproductive stage of the protozoan organism, which grows fastest at around 42°C and proliferates by binary fission. In their free-living state, trophozoites feed on bacteria. In tissues, trophozoites phagocytize red blood cells and white blood cells and destroy tissue.

Cyst Stage: Trophozoites encyst due to unfavorable conditions. Factors that induce cyst formation can include food deprivation, crowding, desiccation, accumulation of waste products, and cold temperatures.


In humans, N. fowleri can invade the central nervous system via the nose, more specifically the olfactory mucosa and cribriform plate of the nasal tissues. The penetration initially results in significant necrosis of and hemorrhaging in the olfactory bulbs causing primary amoebic meningoencephalitis (PAM or PAME). PAM is a syndrome affecting the central nervous system, characterized by changes in olfactory perception (taste and smell), followed by vomiting, nausea, fever, headache, and the rapid onset of coma and death in two weeks.

It is found worldwide, most commonly, in:

  • Warm bodies of fresh water, such as lakes, rivers
  • Geothermal water such as hot springs
  • Warm water discharge from industrial plants
  • Minimally chlorinated swimming pools
  • Soil

Intermediate organism in Naegleria fowleri life cycle (see CDC diagram)

Wuchereria Bancrofti

Wuchereria bancrofti or Filaria, is a parasitic filarial nematode worm spread by a mosquito vector. It is one of the three parasites that cause lymphatic filariasis, an infection of the lymphatic system by filarial worms. It affects over 120 million people, primarily in Africa, South America, and other tropical and sub-tropical countries

W. bancrofti largely affects areas across the broad equatorial belt (Africa, the Nile Delta, Turkey, India, the East Indies, Southeast Asia, Philippines, Oceanic Islands, Australia, and parts of South America.)

The mosquito vectors of W. bancrofti have a preference for human blood and it appears that humans are the only animals naturally infected with W. bancrofti. There is no reservoir host.

Obstructive (Chronic) Phase: Marked by lymph varices, lymph scrotum, hydrocele, chyluria (lymph in urine), and elephantiasis. Microfilariae are not normally present in this phase. A key feature of this phase is scar formation from affected tissue areas. Other features include thickening of the skin and elephantiasis, which develops gradually with the attack of the lymphatic system. Elephantiasis affects men mainly in the legs, arms, and scrotum. In women, the legs and arms are affected.
The severe symptoms caused by the parasite can be avoided by cleansing the skin, surgery, or the use of therapeutic drugs, such as Diethylcarbamazine(DEC), ivermectin, oralbendazole.

Ascaris lumbricoides

Ascaris lumbricoides is the giant roundworm of humans, belonging to the phylum Nematoda. An ascarid nematode, it is responsible for the disease ascariasis in humans, and it is the largest and most common parasitic worm in humans. A quarter of the human population is estimated to be infected by this parasite. Ascariasis is prevalent worldwide and more so in tropical and subtropical countries.Ascaris lumbricoides, or "roundworm", infections in humans occur when an ingested infective egg releases a larval worm that penetrates the wall of the duodenum and enters the blood stream. From here, it is carried to the liver and heart, and enters pulmonary circulation to break free in the alveoli, where it grows and molts. In 3 weeks, the larvae pass from the respiratory system to be coughed up, swallowed, and thus returned to the small intestine, where they mature to adult male and female worms. Fertilization can now occur and the female produces as many as 200,000 eggs per day for a year. These fertilized eggs become infectious after 2 weeks in soil; they can persist in soil for 10 years or more.

The eggs have a lipid layer, containing ascarocides and it makes them resistant to the effects of acids and alkalis as well as other unpleasant chemicals. This resilience helps to explain why this nematode is such a ubiquitous parasite.

Most diagnoses are made by identifying the appearance of the worm or eggs in feces. Due to the large quantity of eggs laid physicians can diagnose using only one or two fecal smears.

Infections can be treated with drugs called ascaricides. The treatment of choice is Mebendazole. The drug functions by binding to tubulin in the worms' intestinal cells and body wall muscles. Nitazoxanide and ivermectin can also be used.

Schistosoma mansoni

Schistosoma mansoni is a significant parasite of humans, a trematode that is one of the major agents of the disease schistosomiasis. The schistosomiasis caused by Schistosoma mansoni is intestinal schistosomiasis.

Schistosomes are atypical trematodes in that the adult stages have two sexes (dioecious) and are located in blood vessels of the definitive host. Most other trematodes are hermaphroditic and are found in the intestinal tract or in organs, such as the liver. The lifecycle of schistosomes includes two hosts: a definitive host (i.e. human) where the parasite undergoes sexual reproduction, and a single intermediate snail host where there are a number of asexual reproductive stages.

Karen Silkwood and Erin Brokovich

Erin Brokovich

(February 19, 1946 – November 13, 1974)

Karen Silkwood was a scientist, who worked in a nuclear factory in Oklahoma (The Kerr- McGee plant). She was making plutonium pellets for nuclear reactor fuel rods. She died under mysterious circumstances after investigating claims of irregularities and wrongdoing at the Kerr-McGee plant ( Silkwood's body was found in her car, which had run off the road and struck a culvert. She was pronounced dead at the scene from a "classic, one-car sleeping-driver accident".)It is believed that Karen Silkwood had uncovered numerous violations of health regulations, including exposure of workers to contamination, faulty respiratory equipment and improper storage of samples. She also believed the lack of sufficient shower facilities could increase the risk of employee contamination.Before she died, she was diagnosed with chronic plutonium toxicity. Karen Silkwood was very active in several Worker's Unions and was getting ready to testify and reveal all the violations occuring at the Kerr-McGee plant. It is believed that she was killed to prevent her from testifying against the company. Kerr-McGee's management asserted that she had contaminated herself in order to paint the company in a negative light. It is theorized that her house was broken into, and the plutonium was placed in her home to further contaminate her with intent of causing her death; and at the same time, attempting to frame her for intentionally contaminating herself, so she could not pursue civil compensation from Kerr-McGee for her contamination.

Similarly, Erin Brokovich an American legal clerk and environmental activist was instrumental in constructing a case against the Pacific Gas and Electric Company (PG&E) of California in 1993. The case alleged contamination of drinking water with hexavalent chromium, also known as chromium(VI), in the southern California town of Hinkley. At the center of the case was a facility called the Hinkley Compressor Station, part of a natural gas pipeline connecting to the San Francisco Bay Area and constructed in 1952. Between 1952 and 1966, PG&E used hexavalent chromium to fight corrosion in the cooling tower. The wastewater dissolved the hexavalent chromium from the cooling towers and was discharged to unlined ponds at the site. Some of the wastewater percolated into the groundwater, affecting an area near the plant approximately two miles long and nearly a mile wide. The case was settled in 1996 for US $333 million, the largest settlement ever paid in a direct action lawsuit in US history. Erin Brokovich was very active in several other lawsuits and fights for the protection of the environment and Public health. Just like Karen Silkwood, she was driven for her passion for the environment and for health and they are big Icons for environmentalists.

Three Mile Island Unit 2 Incident

In March 1979, a nuclear accident occurred at the Three Mile Island Unit 2. The incident resulted in the first case of melted fuel in a full scale commerical nuclear power plant. The melted fuel causes thousands of people to get evacuated from Harrisburg, Pennsylvania. The incident was also considered a catalyst for the creation of yet another federal agency. The accident occurred when a small valve failed to close, causing cooling water to drain from the nuclear core. The core quickly began to overheat. Confronted by baffling and contradictory information, plant operators shut off the emergency water system that would have cooled the core. Operators were able to quickly contain the leak, avoiding a serious "meltdown".
Ironically, two weeks earlier, a motion picture called "china syndrome" was released; the movie's story was about the eventuality that an American nuclear plant melts down which would cause the core melt through the Earth until it reaches China. After the catastrophe, the U.S nuclear activity nearly ceased, giving way to extensive fossil fuel used and giving birth to the US dependency on oil.

Nearly thirty years later, environmentalist have started to worry about the active rebirth of nuclear activity in the country for several reasons. Some fear that excessive nuclear activity will create more health issues for residents. Others believe that nuclear energy is the answer because it would significantly reduce the burning of fossil fuels which is believe have a big reponsibility in global warming upsurge in the amount of extreme weather events, such as wildfires, heat waves, and strong tropical storms, is attributed in part to climate change by some experts and is constantly raising the issue of global warming.Between 1970 and 2004, global greenhouse gases significantly. Some environmentalists believe that global warming is a phenomenon due to human activities. They argue that no one has to be an environmentalist to know that those 70% constitute a massive jump in pollutants and a big problem for the effect it has on the planet’s natural temperature. They also believe that it is worse for carbon dioxide; its annual emissions grew by about 80 per cent between the same period. The also argue that our society releases too much carbon dioxide into the atmosphere much faster than plants and oceans can absorb it. Therefore, they believe that nuclear energy is the answer to slow down global warming. I personally believe that nuclear energy could solve a lot of energy issues, if used properly and if in he right hands, because research has proven it to be clean, green, and safe. Over the years, global warming and nuclear energy has become a political issue, dividing political parties significantly. Such delicate issues are topics that are not often discussed in classrooms because they stir a lot of passion. In other settings, like healthcare departments, there is a certain way to address these issues because lobbying is not allowed in the Public Health system and professionals have to be careful not to cross the line of advocacy and lobbying.