Ascaris lumbricoides: Biggest you've ever seen

http://diseasepicture.com/ascariasis?pid=94

Introduction: Ascaris lumbricoides is the largest intestinal worm to infect humans. These worms can reach up to 18 inches in length, and survive by ingesting intestinal contents and fluids. These worms are found in areas with poor sanitation and malnutrition. People that have Ascaris lumbricoides have severe gastrointestinal pain caused ascarisis. Symptoms of ascarisis include fever, jaundice, wheezing, and abdominal tenderness due to the movement of worms through intestines. This disease is not a deadly disease but has caused 8,000-100,000 deaths due to gastrointestinal complications, such as ruptures and blockages. [1]

Symbiont Description: Ascaris lumbricoides belongs to the phylum Nematoda, and has a smooth hairless body. The males are relatively smaller than the females. Males are normally 7.8 in while the females are 12 in [2]. The males also differ from the females because their tails have a hook shape and tethered ends. The mouths of A. lumbricoides have three lips with very sharp teeth that assist in attaching to the intestinal wall and movement throughout the body [2].

http://www.nematode.net/NN3_frontpage.cgi?navbar_selection=speciestable&subnav_selection=Ascaris_lumbricoides

Host Description: A. lumbricoides only host is humans, but mostly children. Children have a higher risk of getting infected because they are more likely to play in soil than adults. Also boys are more likely to get infected than girls. When comparing US to the rest of the world, 4 million Americans have been reported to have these worms. On an international level 1.4 billion people have been infected with these worms [1]. Some patients have been known to have only a few worms which are easily treatable. But in some cases there can be hundreds of worms in patients causing extreme pain and gastrointestinal trauma [3].

Life Cycle:
 

http://www.dpd.cdc.gov/dpdx/html/ascariasis.htm



The process starts by coming into contact with A. lumbricoides infective eggs, by ingesting soil or crops that have not been washed properly. Once inside the body the eggs hatch and release larvae to penetrate the intestinal wall. Larvae migrate to the pulmonary system and then to the alveolar area causing the host to cough. After 1-2 weeks a cough allows the larvae to be swallowed and sent in the direction of the small intestines. These larvae mature into adults and lay eggs. The eggs are excreted through the feces. Once the eggs are excreted it takes about 1 week for them to become infective eggs and is able to infect another host. The full process from egg to adult takes 9 weeks [7]. Adult worms can live 6-24 months in a host. Since these worms live in the human body for up to 2 yrs they have been known to migrate to different areas of the body, mostly the nose, mouth, and anus [1]. Some patients have reported waking up with a pillow full of worms. What a way to wake up!!!.

Ecology: A. lumbricoides are found in tropical and subtropical areas because of the humid and warm conditions that aid in the survival of the eggs. These worms have also been reported in areas where human waste is used as fertilizer, and in the southeast areas of the US. Most infections happen in Latin America (8%), Africa (12%), and Asia (73%) [3]. Treatment of this disease for acute cases is through albendazole, ivermectin, or mebendazole. These medications work by killing the adult worms. In major cases, more than 20, surgery is needed to excrete the worms from the body and repair the damage they have caused [4] [5].

An example of Ascaris lumbricoides: This is an example of how a parasite has a complex life cycle to survive in the human body. The larvae have to develop in a secure area, alveolar area, so that they can grow to withstand the acid of the stomach. Since this process takes up to 9 days this is important. If the larvae try to leave to quickly they can be destroyed by the stomach acid. The complex life cycle also increases fitness because the females are able to reproduce and lay eggs that are able to infect another host, which in turn keeps the cycle going.

References :

[1]- http://emedicine.medscape.com/article/788398-overview

[2]- http://chestofbooks.com/health/disease/Intestines/Ascaris-Lumbricoides-Common-Spool-Or-Round-Worm.html

[3]- http://www.humanillnesses.com/original/A-As/Ascariasis.html#ixzz1EElwuXri

[4]- http://www.mayoclinic.com/health/ascariasis/DS00688/DSECTION=treatments-and-drugs

[5]- http://www.metapathogen.com/roundworm/

[6]- http://www.suite101.com/content/ascaris-lumbricoides-life-cycle-a32510

[7]- http://www.dpd.cdc.gov/dpdx/html/ascariasis.htm