February 10 - Ascaris lumbricoides

Adult Ascaris lumbricoides, the most common nematode parasite of humans, live in the small intestines. Their eggs are passed in feces, with those finding their way into contaminated food capable of infecting new unwary diners. Once eggs are swallowed, stomach acid and bile release the larval worms in the small intestine. You might think that they’d be sensible and just grow up there, completing the infection cycle. Nope! The larval worms leave the intestine, burrowing through the mucosa and get picked up by circulating blood. Those that don’t get lost in random tissues are carried to the lungs where they break out into the alveolar spaces, migrate up the trachea, or are coughed up, whereupon they are swallowed and arrive right back where they started, growing up to become reproductive adults in the small intestine - not unlike going from the White House to the Capitol Building via a side trip to Philadelphia!

As bizarre as their migration might seem, there also are bizarre human stories surrounding these amazing worms. In 1922, Shimesu Koino ate 2000 eggs of Ascaris lumbricoides, and fed 500 Acaris suum eggs from pigs to his younger brother! Koino didn’t fare so well, but he did demonstrate the pulmonary syndrome associated with early Ascaris infections. He also inferred the route of migration by finding larvae in his sputum. In 1970, annoyed that his roommates were bugging him to pay his rent on time, a postdoc at McGill University in Montreal, Eric Kranz, laced their food with hundreds of thousands of Ascaris lumbricoides eggs that he had taken from the parasitology lab at Macdonald College. Richard Davis, William Butler, David Fisk, and Keith Fern were each hospitalized and Kranz was charged with attempted murder. Ascaris eggs are extremely resistant to destruction; they remain viable for months to years. In 1920, Yoshido even demonstrated their ability to remain viable in the face of hydrochloric, acetic, and nitric acids or even after they’ve been immersed in formalin – a real danger for biology classes that incorporate dissection of Ascaris in their studies.

Adult female Ascaris lumbricoides have a strong tropism for tight curved spaces that mimic the curved tail of males they must seek out in order to be fertilized by unusual, crawling amoeboid sperm. Alas, this predeliction has more than once revealed an otherwise asymptomatic infection when a female alarmingly crawls her way out through a victim's nostril!

Contributed by Mark Siddall.

February 9 - Monotropa uniflora

Monotropa uniflora, also known as the Indian Pipe plant or the Ghost Plant, is a kind of parasitic plant known as a myco-heterotroph. These plants use the symbiotic fungi that associate with other plants, in this case trees, to get their nutrients. Because they do not need to photosynthesize themselves, they can grow in very dark conditions. At present, there is just a single species described, which has a wide, but highly discontinuous distribution in North America, Central America, and eastern Asia, but a recent paper based on DNA sequences from the plants has suggested that these are distinct evolutionary lineages.

Photo from here.

February 8 - Coelioxys coturnix

A female Coelioxys (Allocoelioxys) coturnix Pérez bee dashes into the nest of another bee species, Megachile minutissima Radoszkowski, and lays an egg on top of her host’s. She has waited—loitering outside the nest while assessing the whereabouts of the other female —for the other’s moment of weakness: leaving the nest to collect the last bit of material to close the brood chamber containing her egg and the pollen and nectar provisions for the larva that will emerge from the egg. Coelioxys coturnix is a cleptoparasitic (sometimes spelled “kleptoparasitic”) bee, an entomological version of the cuckoo bird, that does not collect food or nesting material for her offspring but uses the nests and, in bees, larval provisions of other species. Depending on the species of parasitic bee, its newly hatched larva might have disproportionately large, fang-like jaws to kill the host’s brood, might feed on the host’s egg, or might (in one very unusual species from Florida currently being described) wait until it is almost too late, during its last larval stage, to do away with the competition. Cleptoparasitism has evolved many times among bees using different pathways, according to Jerry Rozen, a Curator at the American Museum of Natural History for nearly 50 years, who has studied these bee species for much of his career.

Contributed by Kristin Phillips.
Photography by Rollin Coville.

February 7 - Legionella pneumophila

In 1976, the nation celebrated the American bicentennial. One event, a convention of members of the American Legion in Philadelphia, had tragic results that led to the discovery of a new pathogenic bacterium. In the weeks following the convention, over 200 people became ill and 34 of them died, triggering public health officials to track down the unknown culprit. The guilty party was Legionella pneumophila, a Gram-negative, rod-shaped bacterium that is both an intracellular parasite of protists (like the ciliate shown here - the long red bits that look like yarn are chains of bacteria inside these cells), and also free-living in the environment, particularly warm, wet places like air-conditioners at convention centers and saunas. People acquire the bacteria when they breathe in vapor containing them, but the disease cannot be spread from person to person. For some, particularly elderly people, people with weak immune systems, and smokers, the bacteria can present a very serious health problem in the form of pneumonia. For others, a milder infection produces what has come to be called "Pontiac fever", named for a similar outbreak that occurred (in all places, amongst county public health department employees) in Pontiac, Michigan eight years before the Legionnaire's convention of 1976. At that point, they could not find the pathogen, but were later able to tie those cases to Legionella pneumophila.

Image from the CDC Public Health Image Library.

February 6 - Triloculatum geeceearelensis

My colleagues Janine Caira and Kirsten Jensen travel around the world collecting tapeworms that live in sharks and skates - their specialty. The diversity of cestodes in these marine creatures is enormous and these two scientists have discovered and described dozens. In a recent paper, they presented a whole new genus of tapeworms from whaler sharks and described five new species. One of my favorites of the pack is Triloculatum geeceearelensis, a species that they found in the finetooth shark, Carcharhinus isodon in the Gulf of Mexico. They named this species after the Gulf Coast Research Laboratory, or "GCRL" to thank the facility for hosting them while they did their work. Sound out the species name and this will make sense! The image is a scanning electron micrograph of the scolex of the tapeworm - the "head" bit that it uses to attach to its host's intestine.

February 5 - Lampsilis fasciola

Mussels may seem like unassuming creatures, hanging out on the riverbed until they’re caught and served with a delicious garlic butter sauce, but many species have parasitic larvae that are crafty and downright aggressive when it comes to attracting their hosts. The larvae, known as glochida, usually can’t move around to seek out their hosts, so they employ a wide variety of lures to bring those hosts to them. Meet Lampsilis fasciola, commonly known as a "pocketbook mussel". The glochidia of this species develop inside their mother for approximately one year, and then the mother mussel moves them to the outside of her shell into a pouch on her mantle. Here’s where it gets interesting. The mantle looks remarkably like a small fish, complete with eyespots, and the movement of the mantle looks like a small fish swimming – just the right meal for a larger fish passing by. When a hungry fish bites the mantle, the glochidia-filled pouch ruptures and the larvae emerge, latching onto the inside of the fish’s gills with adhesive threads and teeth on their shells’ valves. Once in their host, the glochidia encyst and develop into juvenile mussels and then drop down to the riverbed to mature, mate, and get ready to lure the next generation of host fish.

Contributed by Kate Bowell.

February 4 - Fasciolopsis buski

Trematodes, or flukes, usually have complex life cycles involving multiple hosts, one of which is a snail. The giant liver fluke, Fasciolopsis buski, is a common parasite in southeastern Asia, including India and China. Eggs are released in feces where they excyst as miracidia, which infect snails. Further development occurs in the snails, until cercariae leave the snail, transform into metacercariae and attach themselves to water plants such as water chestnuts. Humans (and pigs) become infected if they eat unwashed/uncooked plants. Despite the fact that they are called “giant liver flukes”, they are only about 3 inches long. But, that’s long enough if you’ve got one (or more!) attached to your small intestine.

February 3 - Dermatobia hominis

The tórsalo or human bot fly, Dermatobia hominis, undergoes larval development in the skin of a vertebrate host. They frequently infest cattle, but can use primates, sheep, and other domestic and wild animals. The method by which larvae reach a host is unique among the family Oestridae. Adult female botflies catch a porter, which is commonly a mosquito, and lays eggs on it. This porter then transports the eggs to a vertebrate host during the course of its natural behavior (e.g., blood-feeding). The eggs hatch while the porter is on the vertebrate host, in response to body heat. First stage larvae gain entry to the host through the arthropod bite or hair follicles. In the host, larvae develop through three instars over 1.5 – 2.5 months. The boil-like lesion caused by the developing larvae stays clean through bacteriostatic action in the larval gut. After development, the maggot exits its host, drops to the ground and pupates in soil, emerging 1 – 3 months later as an adult fly.

In the tropics, where botflies are common, people specialize in popping bots (like American teenagers pop a zit). Massaging the site and knowing just when to press is a skill. Some people prepare the area first by applying an oily paste (e.g., petroleum jelly) to the site for several hours; this causes the bot to retract the cuticular spines it uses to hold itself in place and move closer to the surface as they breathe through a respiratory siphon that exits at the skin surface. Although some think that putting a steak on the furuncle caused by the bot will cause the maggot migrate to the other, more attractive, meat source;, the bot only emerges because it's suffocating. So, use petroleum jelly -- it's cheaper than steak! Prior to the extraction in the video, the site was kept under Vaseline and bandages for over a day, which is probably why it came out so easily. Please do not attempt extracting a bot by yourself – see a doctor. You could rip off the respiratory siphon of the larva causing it to die inside of you, where it might become infected - and then you'll have more serious problems than a baby fly temporarily using you as its home.

Contributed by Holly Tuten.
Video by Brandon Mellin, Clemson University.

February 2 - Eimeria monacis

Because today is Groundhog Day, it seemed only fitting to highlight a parasite of Marmota monax, the groundhog or woodchuck. Eimeria monacis is a coccidial parasite – a group of parasites that are thought to be very host specific. Eimeria is an apicomplexan, like Toxoplasma, Plasmodium, and Cryptosproridium. Their life cycle contains many of the same stages and processes, but unlike vector-borne apicomplexans like malaria, Eimeria and other coccidians only use one host and are transmitted from host to host via oral-fecal pathways. (You can see a nice animation of the life cycle here, albeit in a goat, not a groundhog.) The picture is from Frederick Fish's original 1930 description of E. monacis. Fish was a parastiologist from Johns Hopkins University, who caught the type host outside of Washington D.C.

February 1 - Echinococcus granulosis

When people think of tapeworms, they often think of very long ones, like Taenia saginata. Echinococcus granulosis is a tiny tapeworm – tiny, but nasty. The main vertebrate hosts of E. granulosis are canids, where the 5 millimeter-long adult tapeworms live in the small intestine. Eggs are expelled in the dog’s feces, where they are eaten by herbivores such as sheep or deer or rodents. Inside the herbivore, the larvae travel through the intermediate host’s blood and take residence in various organs where they form hydatid cysts, which can grow very large in some cases – as big as a grapefruit or even larger. It is thought that these cysts make the herbivore more vulnerable to predation by – canids, of course. Humans can serve as intermediate hosts if they are exposed to contaminated dog (or coyote or wolf or other canid) feces and will suffer from hydatid disease when the larval tapeforms form cysts in our organs. This can be a serious condition, not only because the large cysts can put pressure on organs, but also because should the cysts rupture within the body, a person can suffer from severe shock. The disease can be common in areas with many sheep.