Necator+Americanus

**TAXONOMIC CLASSIFICATION**
KINGDOM: Anamalia PHYLUM: Nematoda CLASS: Secernetea ORDER: Strongylida FAMILY: Ancylostomatidae GENUS: Nectar SPECIES: N. americanus

BACKGROUND
Necator //americanus// is a species that is commonly known to many as “hookworms” due to the dorsal curve at their anterior end. This parasitic nematode is a soil transmitted helminthes (STH) which is the most common nematode to infect humans and animals such as dogs, cats, and pigs. N. //americanus// infect their host by attaching to their host's small intestinal lining and extracting their host's blood supply. As a result, the human host may develop abdominal pain, diarrhea, weight loss, and iron deficiency or anemia. Infections that occur in children or infants could possibly effect mental and physical development. N. //americanus// has a morbidity rate of 12% and a mortality rate of 0.005%. It has been estimated that about 576 to 740 million people in the world are infected with hookworms. Many N. //americanus// infections or nectorasis, occurs in regions where human feces are used as fertilizers or where people defecate on the soil. This specie is predominately found in the Americas, Africa, and Asia. N. //americanus// are found in tropical regions around the world and vary in size and different mouth structures depending on the geographic location.

BASIC BODY STRUCTURE
Adult N. //americanus// consist of a bilateral cylindrical body structure comprised of a cuticle layer that protects the parasite when invading its host’s digestive tract. This cuticle consists of three outer layers composed of collagen and other substances that the epidermis secretes. The N. //americanus// also has a curved dorsal at the anterior, which is how the parasite acquired its name “hookworm”. For N. //americanus// males, their size is estimated to be about 7 to 9 mm long while females are 9 to 11 mm long. The mouth of this specie has two dorsal and two ventral cutting plates at the buccal capsule. They consist of a pair of subdorsal and subventrical teeth in which allows them to attach to the small intestinal lining and feed off of their host's blood.



FOOD SOURCE
N. //americanus// are sanguivore, blood consumers. While residing in the small intestine, N. //americanus// feed off the blood and nutrients of their hosts. They attach themselves to the intestine walls and cause bleeding by using their cutting plates.

LIFE CYCLE
The life span of a N. //americanus// has been estimated to be 3 to 5 years. Female N. //americanus// produce 5,000 to 10,000 eggs per day that are about 65 to 75 micrometers by 36-40 micrometers in size. These eggs start out as being unembryonated in the soil, many times residing in the fecal matter of infected hosts. Under optimal condition, N. //americanus// eggs become embryonated and hatch, beginning their second stage of life. This stage is referred to as 'rhabditiform'. Rhabditiform lava start to grow and molt in the soil to give rise to their third form, the 'filariform' larva. At this stage of life, N. //americanus// are in their infective form, where they are able to penetrate through human skin, traveling though blood vessel to reach vital organs, the heart and then lung. Once at the lungs, these larvae bore through to the pulmonary alveoli to make their way up the trachea. It is here at the trachea where the larvae are swallowed and brought to the small intestine to mature into adult N. //americanus// by attaching themselves to their host's intestinal lining. As a grow parasite, the N. americanus mate and begin to reproduce. They lay thousands of eggs per day that are expelled into soil through their host's fecal matter allowing the cycle to repeat.



MODE OF TRANSMISSION
Transmission generally occurs through any skin contact with surfaces contaminated with N. //americanus// larva, such as soil or fecal matter. When the skin is exposed to contaminated surfaces, the filariform larvae infects the host by penetrating through the skin and entering the blood stream.

SYMPTOMS
When N. //americanus// larvae penetrate the skin, some symptoms occur are irritation and pain at the area of penetration. An adult N. americanus attaches to the villi of the small intestine and feeds on the host's blood and nutrients to allow it to grow and reproduce. Due to the loss of blood and nutrients in the small intestine, many infected host develop abdominal pain, diarrhea, cramps, loss of appetite and weight loss as well as nausea and headaches. With some heavy infections, many individuals experience, hemorrhage from intestinal wall, anorexia, iron deficiency and hypochromic microcytic anemia because of the massive amount of blood and nutrient loss. It is very rare that ones dies from an N. //americanus// infection but many times, individuals become disabled.

DIAGNOSIS
Individuals can be diagnosed through laboratory test. The main diagnostic method used is the stool ova and parasites test, which examines an individuals feces to detect for the presences of N. //americanus// eggs under a light microscope. To determine the severity of the infection, the eggs are counted and generally a count of more than 200 eggs per gram of feces, indicates a severe infection.

TREATMENT
A N. //americanus// infection can be treated with anthelminthic medication such as albendazole, and mebendazole, which are the treatment of choice. Treatment with anthelminthic medication last up to about 3 consecutive days with the same dosage for adults and children. Many times, iron supplements or high protein diets are required as well for those with hemorrhage or to ensure a faster recovery. In some cases, individuals suffering from severe anemia, due to the infection, may need blood transfusions.

EPIDEMIOLOGY
N. //americanus// are the most common hookworm to cause infection in humans around the world. There is an estimate that 576 to 740 million people in the world are infected with hookworms and 80 million of them are severe cases. N. americanus infections has a morbidity rate of 12% and a mortality rate of 0.005%. Many infections of the N. //americanus// occur in the Americas, sub-Saharan Africa, and Asia. Sub-Sahara Africa and East Asia are known to have the most cases, 198 million and 149 million infections. The N. //americanus// infections are most common in tropic areas with warm and moist temperatures. Infections can also arise in areas where soils is contaminated with human fecal matter and in poverty-stricken areas with poor sanitation.

PREVENTION
In order to minimize the number of N. //americanus// infections from occurring, educating individuals in high- risk area about the parasite and improvements on sanitation and hygiene will enable individuals become more aware and enable them to take precautions to reduce their chances of contacting the parasite. Also with proper disposal of human feces, it would help reduce the spread of this parasitic infection due to containing the contaminated fecal matter in one location. Another method to reducing the number of N. //americanus// cases is by providing mass treatments to communities in regular intervals to assist in the reducing the spread of the infection and also the contamination of soil.