Works Cited
Hopkins,
D. R., Foege, W. H. 1981. Guinea Worm Disease. Science, Vol. 212, No. 4494. 495.
Manson, P.
1895. On The Guinea-Worm. The British Medical Journal, Vol. 2, No. 1822. 1350-1351
Friday, October 12, 2012
The weird and wonderful life of Dracunculus medinensis
Unlike many other parasites which are spread through directly contaminated food and water or transmitted by biting insects, Dracunculus medinensis has an intriguing life cycle involving harmless copepods and worms bursting from the skin. The nematode starts it's life as a free-floating egg in a body of water, usually a pond or a slow moving river. The egg eventually hatches and the larvae is ingested by copepods of the Cyclops genus as they comb the water for food. Once inside the unsuspecting crustacean, the larvae will mature into it's infective stage within approximately 14 days. The larvae will live inside the copepod until a human host comes along. If the person is gathering drinking water and they happen to scoop up some infected copepods, they can easily become infected if the water is not treated beforehand. When ingested, the infected copepod will be broken down by the digestive system, allowing the nematode larvae to escape into the intestines of the human (Potter). There it will penetrate the intestinal lining and migrate to subcutaneous tissue by traveling through the lymphatic system. The worm will slowly mature within the host until they reach their adult stage within a year (Hopkins 1981). Assuming both male and female worms are present within the host, the worms will mate once reaching adult stage. The males then die and are broken down by the body. The females, however, will make their way into extremities, often the legs, and move closer to the skin.. There they will create an pustule on the skin, which will eventually burst into a small ulcer, often with the female worm's head at the center. There the worm will wait until the host comes in contact with water. When the when the infected human exposes their affected limb to water, such as by walking into a pond for drinking water collection, the female worm will release its eggs (Manson, 1895). The worm usually creates a severe burning sensation when forming the pustule on the skin, and the host is likely to scratch at it and put the limb in water to help with the pain. This often allows the worm quicker access to water. After the eggs are released, they will hatch and once again be ingested by copepods.
Works Cited
Works Cited
Using Pseudacteon’s Aggressive Behavior for Biological Control Methods
Pseudacteon, part of the Phoridae family, is an extremely diverse group which
contains over 25,000 species. The life
cycle of Pseudacteon begins with a female fly injecting a single egg into the thorax of a
fire ant through an aerial attack. Each female Pseudacteon has the ability to produce about 100 - 300 eggs during her lifetime. The female injects its egg into the ant using a ovipositor. There are three main instars for the larva, during which the ant still functions normally. During
the second instar, the fly larva migrates into the head of the ant and procedes pupariation. During pupariation, the fly larva consumes the head capsule tissue of the ant. This forces decapitation and the larva can now complete development inside the head of the ant. The pupa forms in the head capsule and an adult phorid fly emerges. The newly born Pseudacteon phorid fly searches for a Solenopsis red fire ant to infest as its host. Pseudacteon
phorid flies are extremely host specific, as they only attack species of red
fire ants. Pseudacteon are widely distributed in the range of their host
species, the red fire ant.
The invasive Solenopsis red fire ant has become an
ecological problem around the globe. They
are beginning to overpopulate and intrude on natural habitats. Pesticides were an attempted method to control their
invasion. However, this did nothing but
spread them even more. These invasive ants have detrimental effects on native
invertebrate and vertebrate species. A new approach was introduced to regulate
this issue. Using the parasitic Pseudacteon
phorid flies as a fire ant predator has become a successful technique. This species is an excellent organism to use
for biological control purposes since they are specific to their host and their
impact is sufficient enough to the point where ants are beginning to develop
phorid fly specific defense behaviors. The use of Pseudacteon as a biological control agent is mainly popular in the
southeastern United States, since those areas have the highest amount of
invasive Solenopsis red fire ants.
Bibliography
Morrison, Lloyd W.
"Biological Control of Solenopsis Fire Ants by Pseudacteon Parasitoids:
Theory and Practice." Biological Control of Solenopsis Fire Ants by
Pseudacteon Parasitoids: Theory and Practice. N.p., n.d. Web. Oct. 2012.
<http://www.hindawi.com/journals/psyche/2012/424817/>.
Porter, S. "Host Specificity and Risk Assessment of Releasing the
Decapitating Fly Pseudacteon Curvatus as a Classical Biocontrol Agent
for Imported Fire Ants." Biological Control 19.1 (2000): 35-47. Science Direct. Web.
Taenia solium:The Never Ending Cycle
Dear Mom and Dad,
My research on Taenia
solium in Japan has moved to Mexico. As globally distributed disease, Taenia solium has the ability to impact
almost anyone. More research on the life cycle and how people get infected must
be done to prevent it or create immunity towards it. In the life cycle of T. solium, humans are the definitive
host, passing eggs (gravid proglottids) through their feces and surviving up to
months in the environment (CDC et al., 2008). Pigs become infected with the
eggs when they ingest the plants from the environment. Oncospheres hatch in the
pigs intestine and attack the intestinal wall. The oncospheres then travel to
the striated muscle and develop into cysticerci. The cysticercus can survive
for years inside the pig. Humans are then infected by ingesting raw or
undercooked infected pork (CDC et al., 2008). The cycle is repetitious and
hazardous.
In the human intestine, adult Taenia solium tapeworms can grow from to 2-7 meters! The adults
produce proglottids which mature, then detach from the tapeworm and
approximately 6 are passed through the stool per day. The eggs contained in the
proglottids are only released after they are passed through with the feces. T. solium adults on average have 1000
proglittids, but can produce up to 50,000 eggs per proglottid! (CDC et al.,
2008). This is an exponentially growing problem and a continuing circle of
infection that needs more study. Continuing research in Mexico is being done
about the development of Taenia solium
metacestodes in pigs.
A recent study here in Mexico took twelve, two month old
male and female piglets and fed each one 100,000 eggs to infect them. Through
the course of the infection the piglets were humanely killed to be necropsied
(animal autopsy) (Garrido et al., 2007). The piglets were examined thoroughly for
metacestodes. To their surprise they found hemorrhages in the liver and the
small intestine early in the infection, numerous vesicular cysts in the muscles
of the leg, and a parasitic cyst in the right temporal lobe of the right
cerebral hemisphere (Garrido et al., 2007). No metacestodes were found, but is
thought to be due to immunity. The more research that is done about the life cycle
of Taenia solium, the more
understanding we will have about the severity of this parasite. Unfortunately
research is not asexual, it cannot do itself, I have to do it, and so I will
write to you soon!
大きな愛情と関心をもって
Tara
Literature
Cited
Center
for Disease Control and Prevention, 2008. “Lifecycle of Taenia spp.”. http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/S-Z/Taeniasis/body_
Taeniasis_il6.htm
Garrido
G. S., Aluja A. S., F.C. Casas, 2007. Early stages of development of the Taenia solium metacestode in pigs.
Journal of Parasitology 93:2,
238-241.
Pechenik,
Jan. A Short Guide to Writing About Biology. 7th: Longman: Pearson
Education Inc., 2010. 71-81, 146-7, 157-162, 162-191, 194-201, 201-207
Prevalence and Associated Risk Factors of Eimeria in Sheep of Punjab, Pakistan
Given the lack of information about Eimeria elephantuli due to its recent
discovery, the presence and prevalence of Eimeria
in sheep is covered in this article. There are fifteen species of Eimeria which are considered to have the
capability to infect sheep and cause the disease coccidiosis, the most
pathogenic of which are E. ovinoidalis,
E. bakuensis, and E. ahsata (Khan et al. 2011).
Coccidiosis can have a negative impact economically, particularly for sheep farmers whose animals are used for markets with a particular demand such as textiles, due to
the profit loss from animal death, treatment cost, and the cost to take
measures to control the spread of the protozoan. All sheep are vulnerable to
the infection, but lambs are impacted the most by the disease, especially when
they are being weaned off of their mother’s milk (Khan et al. 2011).
Four hundred and eighty six sheep from
Pakistan were observed in the study, with their associated farmers filling out
questionnaires that inquired about perceived risk factors including: age,
breed, sex, climate, and husbandry and management. There were two age groups,
four breeds, four seasons, three feeding systems, two housing systems, two
floor patterns, two watering systems, and two herd sizes created for testing
based on the questionnaires (Khan et al. 2011). The identification of different
species of Eimeria found in the
sampled sheep was based on the morphological features of the oocysts of the
parasite. These features included but were not limited to: size, shape, color, and
texture of the oocyst wall, as well as reference to taxonomic keys (Khan et al.
2011).
Fourty-three percent of the sheep
sampled were infected with some species of Eimeria,
with five different species being found in those sheep. The most common species
was E. ovinoidalis followed by E. ahsata, E. intricata, E. parva,
and E. faurei. The rainy season had
the highest recorded incidence of parasitic infection, with lambs generally
having a higher infection rate than adult sheep (Khan et al. 2011). Statistical
analysis found that the age, sex, season, housing system, floor type, watering
system, and herd size were the factors that were significantly related to the
prevalence of Eimeria infections.
Housing system stood out as being one of the biggest risk factors of infection,
with just over 50% of animals in a closed housing system being infected
compared to the 30% of animals that were infected in an open system of housing
(Khan et al. 2011).
Coccidiosis increases in the post rainy
season because the wet and humid climate is perfect for the parasite to
reproduce. Animals in contaminated quarters, who are overcrowded, or
whose drinking water can be contaminated by fecal matter also have a higher
prevalence of infection compared to those that live in better hygienic conditions
(Khan et al. 2011).
References
Khan,
M., Rehman, T., Iqbal, Z., Sajid, M., Ahmad, M., Riaz, M. 2011. Prevalence and
associated risk factors of Eimeria in
sheep of Punjab, Pakistan. World Academy
of Science, Engineering & Technology. 79: 443-447.
Thursday, October 11, 2012
Humans are Hosts Too
Now that you’ve had several weeks to
utilize your resources at the local library to gather some information on the
mystery coccidian specimens and are attempting to learn the unique language of
science, you’re ready to start analyzing.
You have learned that a coccidian is a specific type of parasite that
causes diseases called coccidiosis and toxoplasmosis, so it is potentially
harmful. You also found that heteromyid
mice are burrowing rodents adapted to desert conditions. (This particular species will probably not be
visiting New England anytime soon, phew!)
They belong to the family Heteromyidae, which includes pocket mice,
kangaroo mice, and kangaroo rats. Ok, so
according to the study in the original article, these organisms cause disease
and are infectious to pocket mice and kangaroo rats from California, New
Mexico, Texas, and Mexico. However, the
three newly described parasites were only found in the mice from Texas.
Cyclospora
angimurinensis
was found in 1 of 20 mice collected for the original study you found (Ford, Duszynski & McAllister, 1990). At the time of the study, there were six
other described species of cyclospora in mammals, all from moles. The new cyclosporan is different in that it
has an oocyst residuum, that is, a mass of cytoplasmic material outside of the
sporocyst and inside of the oocyst. A
sporocyst is the initial lifecycle stage of the parasite. Sporocysts, when inside of oocysts, are the infective stage to mammals and birds. An oocyst is essentially comparable to an egg
of a female. The new cyclosporan
described also has different-shaped sporocysts with different length by width
ratios.
Eimeria
chaetodipi
was found in 3 of 20 mice collected. This
specimen has sporulated oocysts that are shaped like those of Eimeria liomysis, another coccidian
parasite that infects heteromyid rodents, but is smaller. Eimeria
hispidensis was found in 4 of 20 mice.
This species has sporulated oocysts that are also similar to E. liomysis, but has an oocyst residuum
that is not found in E. liomysis.
Heteromyid rodents nest in underground
burrows in which no more than one individual typically resides. Its fecal matter is deposited in side tunnels
away from the burrow. This separation of
territory could limit heteromyids from coccidian exposure, and infection
prevalence is consequently moderate.
Heteromyids inhabiting the plains and prairie regions of the midwestern
United States seem to have a high prevalence of infection due to greater
amounts of humidity and precipitation unlike those inhabitants of desert areas (Ford, Duszynski & McAllister, 1990).
Some of the reported coccidians of
heteromyid rodents are host-specific while others are not, which could be due
to unique morphological and biochemical properties of the rodents or the
diverse host range of coccidian parasites.
It appears that the three described species of coccidians are not much
to worry about as they like warmer, humid climates and are partial to small
mammals (Ford, Duszynski &
McAllister, 1990). On another note, the “diverse host
range” sparks your interest, especially when you stumble upon a massive listing
of hosts, unfortunately including humans and domestic animals under the mammals
section (Duszynski, Upton & Couch, 1998).
Looks like you’re going to have to hit the books again and find out
about the pathology and lifecycles associated with the human and pet species of
coccidia.
References
Ford, P. L., Duszynski, D. W., &
McAllister, C. T. (1990). Coccidia (apicomplexa) from heteromyid rodents in the
Southwestern United States, Baja California, and Northern Mexico with three new
species from Chaetodipus hispidus. Journal
of parasitology, 76(3), 325-331.
Duszynski, D.
W., Upton, S. J., & Couch, L. (1998). The coccidia of the world.
Retrieved from http://biology.unm.edu/biology/coccidia/table.html
Heart and Filarial Worm
Dirofilaria
immitis is a pathogenic heartworm responsible for feline heartworm disease. To
study this heartworm, scientists rely on shelter animal autopsies. Though this
heartworm is seen in both cats and dogs, it is much more prevalent in dogs. In Yabsley et al.’s experiment they studied
shelter dogs and cats in northwestern South Carolina to determine the threat of
heartworm infection for dog and cats living in that area (Yabsley et al., 2004).
It was discovered that the dogs infected with D. immittis were also infected with D. reconditum which is a nonpathogenic filarial worm. According to
Chalifoux and Hunt’s study, a noteable difference between the two are that D. immitis shows enzyme activity in
excretory and anal pores whereas D. reconditum shows uniform enzyme activity (Chalifoux,
Hunt, 1971).
Though they are oftentimes found
together, the two parasites are quite different. D. reconditum finds a definitive host in dogs through the
intermediate host Ctenocephalides felis
(a flea) and Heterodoxus spiniger
(lice) (Nolan, University of Pennyslvania).
D. immitis is more versatile,
finding dogs, foxes, wolves, coyotes, and cats all good definitive hosts and
lives in the right chamber of the heart as well as pulmonary arteries of its
host (Ferris, 1999). Aside from their hosts and enzymatic activity,
morphologically D. immitis and D. reconditum differ in head shape, tail
shape, and body movement. Though their differences do not seem large, as we
have all learned in entry level biology, shape can absolutely determine
function. I would venture to assume that the seemingly subtle differences
between these two parasites may be why one is pathogenic and one is not.
Works Cited
Chalifoux, Laura, and Ronald
Hunt. "Histochemical Differentiation of Dirofilaria Immitis and
Dipetalonema Reconditum." Journal of the American Veterinary Medical
Association 158.5 (1971): 601-05. Print.
Ferris, Howard.
"Dirofilaria Immitis." Nemaplex. University of California,
n.d. Web. 11. Oct. 2012
Nolan, Tom and Kim Mah.
"Dipetalonema Reconditum Homepage." Diagnosis of Veterinary
Endoparasitic Infections. University of Pennsylvania, 2004. Web. 11 Oct.
2012.
Yabsley, M. J., C. Dresden-Osborne, E. A.
Pirkle, J. M. Kirven, and G. P. Noblet. "Filarial
Worm Infections in Shelter Dogs and Cats from Northwestern South Carolina,
U.S.A." Comparative Parasitology 71.2 (2004): 154-57. Print.
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