March 31 - Spinochordodes tellinii

Ever seen a grasshopper jump into a pool? Probably not. The reason is normal, healthy individuals would never take a dive to almost certain death. Spindochordodes tellinii on the other hand, has different intentions. This parasitic nematomorph hairworm is able to override the grasshopper’s instinct to stay out of water. Spindochordodes tellinii larvae are consumed by grasshoppers or crickets and develop inside their hosts. The hairworm can grow to enormous lengths yet allow the grasshopper or cricket to stay alive. The exact process S. tellinii uses to manipulate its host is still largely unknown. We do know that the parasite produces proteins that affect the central nervous system and that infected grasshoppers/crickets also produce different proteins in their brains which healthy individuals do not. Mature adult S. tellinii use their abilities to force their host to jump into some body of water allowing the parasite to escape to find a mate. Understanding how parasites can manipulate behaviors of other organisms may help us to further understand human behavior-system links.

See: Bhattacharya, S. 2005. Parasites brainwash grasshoppers into death dive.

Contributed by Zander Crawford, Bucknell University.

March 30 - Loa loa

Loa loa, also known as the “eye worm,” gets its name from an affinity for subcutaneous tissue like the tissue found in human eyes. This nematode parasite finds its way into humans through the deer fly, in which the Loa loa worm larvae develop. Once in its third stage, a larva can enter a human when a deer fly bites. When larvae mature within subcutaneous tissue, they produce microfilariae – an uninfective stage of the Loa loa, which are then picked up by other deer flies. These parasites can be removed surgically, but drugs are required to kill microfilaria within the bloodstream. Adults can survive in subcutaneous tissue for up to 17 years, and take one year to fully mature. The first recorded case of Loa loa dates back to the year 1770 when a surgeon failed to remove a worm in a woman’s eye in the Caribbean. Loa loa was again found in slave ships coming to America. Loa loa has not been diagnosed in the United States in almost a century, but the parasite is still endemic to western and central Africa. While not fatal, Loa loa can be a complication for patients with other diseases. These microscopic worms are hard to see, unless they’re in your eye.


References:
1. Loa loa: A cutaneous filarial parasite of humans. Filarial Biology.
2. Muller, R. Worms and Human Disease. New York: CABI, 2002.

Contributed by Prath Devre, Bucknell University.

March 29 - Naegleria fowleri

Naegleria fowleri is a protist that seems to be straight out of science fiction. Ranking at number five on the Science Channel’s "Top Ten Infectious Diseases", N. fowleri is a free-living amoeba capable of devouring your brain! This insidious creature makes its home as a flagellated amoeboid in characteristically warm freshwater sites such as lakes, rivers, geothermal hot springs, warm water discharge from industrial plants, poorly maintained and minimally-chlorinated or unchlorinated swimming pools and Jacuzzis. However, it has also been documented that it can be contracted by the inhalation of dust containing its cyst form, and has been isolated in places such as soil or air conditioning units. Although it prefers warm conditions that can reach up to 46°C, N. fowleri can endure winters by becoming cysts that settle into bottom-lying sediment. Capable of parasitizing a variety of mammals, including humans, the amoeba causes primary amebic meningoencephalitis (PAM), a fatal disease that has been recorded as the cause of death in over 150 worldwide cases reported. In all of these cases, the victim of this lethal microbe died within two to three days of infection. Infection occurs almost exclusively through the olfactory tract whereupon it migrates to the brain or spine of its host by traversing the olfactory nerve. It then feeds upon brain tissue and blood cells as an amoeboid trophozoite via phagocytosis and pinocytosis. Thankfully, it isn’t contagious between hosts.

Contributed by Jameson Clarke, Bucknell University.

March 28 - Wuchereria bancrofti

Wuchereria bancrofti is a nematode parasite found in Africa, South America, and tropical and sub- tropical countries in other locations. This worm uses two hosts: mosquitoes and humans. The microfilarias inhabit a mosquito until they grow into their motile larvae stage. They then move on to a human host; being transmitted during the blood meal of the mosquito. While in the human host they move to the lymph nodes over the course of a year where they then develop into the adult worm stage. Adult worms live 4-6 years in their host and produce millions of microfilaria which make their way into the circulatory system from the lymph nodes. This parasite can cause permanent damage to both the kidneys and the lymphatic system. Damage to the lymphatic system can cause a disease known as lymphatic filariasis in which the lymphatic system stops working properly and the lymph nodes become enlarged. It is estimated that 120 million people in 80 countries have suffered from filariasis. Untreated, this could lead to elephantiasis, a thickening of the skin and tissues which produces large growths on the body. Some drugs have been found that kill these parasites but only in their developmental stage. No current treatments have been found to eliminate adult parasites.

Contributed by Laura Rycek, Bucknell University.

March 27 - Haemobaphes diceraus

Haemobaphes diceraus is a parasitic pennellid copepod that is found on a variety of fish species. This is an interesting species because it is a type of crustacean and many people would never think of a crustacean as a parasite. It is also an interesting parasite because it looks nothing like a crustacean in its adult form. This parasitic copepod extends from the gills and into the bulbous ateriosus of the heart where the parasite is anchored. The distinguishing feature of this parasite is the large, spirally coiled egg sacks. These egg sacks project from the gill arch of the host fish. The egg sacks are attached to a trunk which extends into the heart. While some copepods are able to move about freely, this copepod has reduced segmentation and appendages in its adult form (Goater 1996). When the eggs hatch they are released into the water where they undergo a series of molts until they are developed enough to find a host. Pennellids such as the Haemobahes diceraus are unique in that they require an intermediate host. After fertilization of the egg the newly hatched parasite has a free swimming phase. It then locates a fish, attaches itself and grows to adulthood. (Goater and Jepps 2002).

References:
Goater, Tim. 1996. “Parasitic Copepoda.”
Goater, T. and Jepps, S. 2002. Prevalence and Intensity of Haemobaphes diceraus (Copepoda: Pennellidae) from Shiner Perch, Cymatogaster aggregata (Embiotocidae). Journal of Parasitology 88: 194-197.

Contributed by Taylor Phillips, Bucknell University.
Image from this site.

March 26 - Trichuris trichiura

Trichuris trichiura is a parasite found in human intestines. Also known as the human whipworm, this parasite’s adult and larval forms can live in the large intestine for up to 5 years, feeding on intestinal tissue secretions. These roundworms are pinkish-white in color and resemble a whip in shape and movement. Females lay 2,000-10,000 larvae per day, which are shed in human feces. With the right amount of moisture and warmth, in 2-3 weeks these eggs become infectious. Humans may become infected by accidental ingestion of eggs from fecal contaminated soil. Infectious eggs are sometimes found in water or in dry foods such as rice, grains, vegetables, and beans. Once ingested, the eggs hatch and burrow into the wall of the small intestine where they grow. About 300-500 million people are infected worldwide, mostly located in tropical places. Diagnosis occurs when eggs are observed in patients’ feces. Although rare in the U.S., people who do not dispose of human waste properly, have poor hygiene, and children playing in dirt contaminated with animal feces are especially prone to the disease. Recent studies have also shown that people with trait characteristics in chromosomes 9 and 18 may also be susceptible. Humans with over 100 parasites may have symptoms associated with intestinal disease. Very serious cases may cause diarrhea, vomiting, loss of appetite, constipation, blood loss, anemia, rectal prolapse, inflammatory and toxic damage to intestines. Medication as well as anti-parasitics are effective to promote healing.

Contributed by Allison Gittings, Bucknell University.
Image from the CDC Public Health Image Library.

March 25 - Sarcoptes scabei

In the aftermath of the earthquake, aid workers report that scabies has been running rampant in tent cities in Haiti. Scabies is a contagious disease caused by Sarcoptes scabiei, parasitic mites that are hosted on humans, dogs, cats, and other wild animals such as koalas, gorillas, and wild boar. Sarcoptes scabiei are Acariformes, members of the subclass Arachnida (spiders, scorpions, mites and ticks), subphylum Cheliceriformes, phylum Arthropoda. Up to 104 species are known to have been infected with Sarcoptes scabiei, producing a condition called sarcoptic mange. All four stages of the parasite’s life, egg, larva, nymph and adult, take place on the host’s epidermis. The adult female burrows under the skin and lays 2 or 3 of her eggs each day. To enter the skin, the mites use cutting mouth parts and cutting hooks on the legs. As the life cycle progresses, the mites come to the surface of the skin, then burrow into molting patches to complete the stages. Burrowing mites feed on living cells and tissue fluid. The first hosts of S. scabiei are thought to have been humans. The mites then infected domestic animals that later transferred the parasite to wild animals. The movement of the mites into and on the skin produces an allergic reaction and is extremely itchy. On humans, scabies is most common in areas of the body that come in contact with the skin of other humans, such as the hands and arms. Scabies can be treated with prescribed medical cream.

Contributed by Sara Baughn, Bucknell University.

March 24 - Dracunculus medinensis

Dracunculus medinensis is a creature in the phylum Nematoda that is behind the dreaded Guinea Worm Disease. The disease is actually caused by the significantly bigger female nematode. Their life starts off with the larvae living inside of small crustaceans (copepods). When a human drinks unfiltered water, they are incidentally ingesting these small crustaceans and this is the beginning of Guinea Worm Disease. Shortly after being ingested, the small crustaceans die and release the nematode larva, which then penetrates the host stomach, intestinal wall, and enters the abdominal cavity. After reaching maturity, which takes about a year, the males die and the females survive and start to migrate through the subcutaneous tissue layer towards the surface of the skin. At this point, the female can emerge from any part of the body including the head, torso, upper body, buttocks, and genitalia, although the bottom of the foot is where they emerge from most of the time. On the bottom of the foot, the female causes painful blisters which cause the host to look for a form of relief by placing their foot into water. When the female parasite comes into contact with water, she will release her larvae which are then injested by small crustaceans and after two weeks the larvae become infectious and the cycle is ready to begin again. As a side note, the only way to remove the parasite is to pull it out through the hole it has made in the surface of the skin. OUCH!!!

References:

http://www.wrongdiagnosis.com/artic/facts_about_dracunculiasis_guinea_worm_disease_cdc_oc.htm

http://www.cmaj.ca/cgi/content/full/170/4/495

Contributed by Tracey Brooks, Bucknell University.

March 23 - Argulus foliaceus

Argulus foliaceus, also known as the common fish louse or the carp louse, is actually not a louse or even an insect at all, but a crustacean. Within the class Maxillopoda, the subclass Branchiura consists of about 150 species of freshwater and marine fish ectoparasites. The genus Argulus is found throughout the world. Argulus foliaceus is native to Europe, but is also common on aquarium and pond fish worldwide. Although the louse shows some host preference, especially for carp, it is usually considered a generalist and is found on a variety of fish species. The oval-shaped, flat adults attach to fish hosts using hooked suckers. They inject digestive enzymes into the host and feed on blood and tissue fluids. Symptoms of lice infestation include abnormal swimming, rubbing, and deteriorating physical condition. Because of tissue damage caused by the parasite, secondary bacterial and fungal infections frequently occur. Adult females leave their hosts and lay eggs on vegetation or other submerged objects. Adults can live free of hosts for two to three weeks, but newly hatched larvae only survive a couple of days if they do not find a host. Treating an infested aquarium may require several approaches, so prevention is best. Always visually inspect and quarantine new fish. Lice may be removed from fish manually with forceps. Fish should be transferred to an alternate aquarium while chemical treatments are used to kill remaining adults, larvae, and eggs.

Contributed by Elizabeth McCarthy, Bucknell University.
Photo from this site.

March 22 - Cotesia congregata

Few species exhibit behavior as gruesome and horrifying as the parasitic wasp, Cotesia congregata. As the great naturalist Charles Darwin once wrote, “I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae [one group of parasitic wasps] with the express intention of their feeding within the living bodies of Caterpillars.” Cotesia congregata belongs to this superfamily of Hymenoptera and their sinister life cycle begins when the adult female oviposits up to eighty eggs, as well as a host of symbiotic viruses, into the body of a young tobacco hornworm While the viruses suppress the caterpillar’s immune responses, the wasp larvae will hatch and undergo a series of molts within the caterpillar. Feeding on the host’s bodily fluids, but carefully avoiding any damage to the vital organs, the mature larva will eventually eat through the caterpillar’s skin and find a nearby branch on which to build a cocoon. At this point the hornworm, remarkably still alive, will arch over the cocoons and vigilantly stand guard over the brood. The host will remain in this position without moving or eating until the wasps have all emerged from their cocoons. The caterpillar will sometimes go so far as to spin a protective layer of silk over the pupae as they grow and voraciously defend the cocoons from predation. The mechanism by which the Cotesia wasps control the host’s strange behavior is not fully understood. However, because a few larval Cotesia remain behind (staying within the host) during pupation, popular theory has implicated them as the primary forces dictating the host’s behavior.

See more in: Zimmer, Carl. Parasite Rex. New York: Simon & Schuster, 2001.

Contributed by Phillip Zook, Bucknell University.

Thanks to Alex Wild for the photo.