Leishmania Equatorensis

In this study, Grimaldi et. al. (1992) describes a new species of Leishmania, Leishmania equatorensis, that was discovered within the liver and spleen of both a sloth and squirrel that were captured in Naranjal, Ecuador in 1982.  In humans, Leishmania is responsible for causing the disease Leishmaniasis, which has three forms.  There is visceral leishmaniasis, which infects mostly the liver and spleen, cutaneous leishmaniasis, which infects the skin, and muco-cutaneous leishmaniasis, which infects the mucous membranes.  All three forms are caused by a different species in the genus Leishmania.  The new species described in this paper was determined to be most closely related to Leishmania braziliensis, which is responsible for muco-cutaneous leishmaniasis, also known as espundia.  L. equatorensis was determined to have the same behavior as L. braziliensis, in terms of its virulence (its ability to cause disease) and the way it develops inside of lab animals.  The hamsters that were exposed to  L. equatorensis developed swelling and eventually lesions on the nose, in anywhere from one to three months time.  This is identical to how L. braziliensis acted.  L. equatorensis was determined to be a new species by the differences in the molecular make-up compared to other species of Leishmania. 

            The original description of this parasite does not answer many questions about the parasite itself.  Two of the big questions raised from the original description are, first, is it dangerous to humans, and second, what is the sand fly vector for this parasite?  Being a new species of the L. braziliensis complex (a species complex being organisms that can’t reproduce with each other but are almost identical in every other way) means that L. equatorensis may be dangerous to humans.  L. braziliensis causes espundia, which can lead to lesions that cause deformities around the nose and mouth.  It can also be fatal if the disease spreads to the larynx and trachea where it may cause septic bronchopneumonia (Garnham, 1971).  Being so closely related, it’s possible that L. equatorensis may cause the same symptoms and complications, and may also be deadly.  If it is harmful to humans, it’s good that it was discovered in these reservoir hosts, and no humans have been infected yet.  This gives researcher’s time to get a better understanding of the organism to hopefully prevent the transmission to human’s altogether.  Because this species is so closely related to L. braziliensis this may be a good reason to look for a decent cure for espundia.  Currently antimony is used to try and kill the parasite but this is also very toxic to humans (Hepburn, 2000).  If more species are being found that could potentially be dangerous to humans, a better treatment may want to be sought out.      

http://www.scielo.br/pdf/mioc/v87n2/vol87(f2)_052-059.pdf

Garnham, P.C.C.  1971.  American Leishmaniasis.  Bull. Wld. Hlth. Org.  44:  521-527. 

Grimaldi, G., Jr., R.D. Kreutzer, Y. Hashiguchi, E.A. Gomez, T. Mimory, and R.B. Tesh.  1992.  Description of Leishmania equatorensis SP. N. (Kinetoplasida: Trypanosomatidae), a new parasite infecting arboreal mammals in Ecuador.  Mem. Inst. Oswaldo Cruz.  87: 221-228.

Hepburn, N.C.  2000.  Cutaneous Leishmaniasis.  Clinical and Experimental Dermatology.  25: 363-370.    

Kelsey's wonderful Pseudacteon flies

A new North American species of Pseudacteon, Pseudacteon gracilisetus, was first found parasitizing Nylanderia arenivaga in June of 2009. Pseudacteon gracilisetus are a parasitic phorid fly that uses Nylanderia arenivaga (“fire ants”) as its host.  P.gracilisetus are found in randomly distributed areas around the United States including, South Carolina, New Jersey, Florida, Nebraska, and Texas.  Not far from a dirt road, female P.gracilisetus were found harassing the fire ants in a dive attack fashion.  The fire ants attempted to fight back but the P.gracilisetus attacked by diving onto the ant and injecting their eggs into the thorax of the ant’s body in less than one second.  The body of a P.gracilisetus parasite is locked with the body of the fire ant, allowing the eggs to be precisely placed inside the ant’s thorax.  Once the eggs hatch inside the ant, the maggots move into the head of the host and develop for 2-3 weeks.  Inside the head of the host ant, the maggot excretes a chemical which dissolves the host’s body, with only the head remaining.  The maggot eats everything in the head of the host and pupates, taking over the head cavity. The new fly is then born from the head of the ant.

            There are 62 species of Pseudacteon and an estimated 20 of those species attack an invasive ant species called Solenopsis invicta.  This particular ant species invaded into North America from South America.  Pseudateon can benefit a biological community by helping control invasive ant species.  Fire ants such as Solenopsis invicta, are an invasive species that cause harm to humans, animals, and livestock.  Since Pseudacteon gracilisetus is native to North America, researchers are introducing these ant parasitizing creatures into South America in attempt to eradicate their native fire ant population. With further research on Pseudateon, researchers can find ways to use parasites to help control invasive species.    

Below is an attached video displaying the attack of Pseudacteon on fire ants: 

http://www.youtube.com/watch?v=6UThaL-D6U8

Brown, Brian V., Scott A. Schneider, and John S. LaPolla. "A New North American Species of Pseudacteon (Diptera: Phoridae), Parasitic on Nylanderia Arenivaga (Hymenoptera: Formicidae)." Annals of the Entomological Society of America (2010): 37-38. BioOne. Web.

Steyskal, George. "A NEW ANT-ATTACKING FLY OF THE GENUS PSEUDACTEON, WITH A KEY TO THE FEMALES OF THE NORTH AMERICAN SPECIES (DIPTERA, PHORIDAE)." OCCASIONAL PAPERS O F T H E MUSEUM OF ZOOLOGY (1944): n. pag. Deep Blue. University of Michigan Library. Web.

Determining Potential Vectors and Potential Hosts.

Jones and Woo provided us with some very useful information about the transfer of Trypanosoma catostomi. Delving deep into their work, one can discover a world of vector biology as well as host specificity and how closely related intermediate hosts may aid in the effect transfer of parasites upon a definitive host or lack thereof. Specifically, T. catostomi infects various species of fish in North America. Up until the work of Jones and Woo, it was unknown which species of fish play host to T. catostomi and which vectors are most effective in the transfer of this trypanosome.

            Jones and Woo cultured T. catostomi on a blood agar medium, and used their cultures to inoculate (mechanically introduce) potential definitive host species of fish, as well as potential vectors (leeches). The researchers determined that Actinobdella inequiannulata allowed metatrypanosomes to develop in their proboscis sheath. These metatrypanosomes (which were deemed to be T. catostomi) were infective to the white sucker fish (Catostomus commersoni) when the fish were both fed upon by A. inequiannulata and when the fish were inoculated with them. Two leeches which are vectors of other flagellate species were also observed to see if they would pose as effective vectors of T. catostomi however both potential vectors did now allow the complete development of the trypanosome which therefore inhibited the infection of white suckers when they were fed upon.

            Ultimately, this work determines that it is indeed helpful to look at the vector to determine what a particular host has been infected with. In the medical field, it may help to narrow down what a possible infection is by looking at exposure of potential vectors. It also poses the question of why certain parasites do not develop to completion within other species of the same genus of the intermediate host. Maybe the answers to this question can lead to eventual immunity of vaccinations to keep pesky parasites out of our bodies. And to think, the year 1992 wasn’t only known for my birthday!

Jones, Simon R. M., & Woo, Patrick T. K., 1992. Vector specificity of Trypanosoma catostomi and its infectivity to freshwater fishes. Journal of Parasitology. 78(1): 87-92.

“The genome of the protest parasite Entamoeba histolytica”

Entamoeba histolytica, as we have learned, is a parasite that mainly infects the intestines and causes amoebiasis. In this article, the authors discuss metabolic adaptations that are shared with two other parasites: Giardia lamblia and Trichomonas vaginalis. E. histolytica reduces and can even completely eliminate metabolic pathways (carbohydrate metabolism, fatty acid oxidation, and urea cycle)¹ as well as, “…the use of oxidative stress enzymes,” (Loftus et al., 856-868). Using the ‘whole-genome shotgun’ approach to sequence the parasite, they found it contains, “…expansions of a variety of gene families, including those associated with virulence." (Loftus et al., 865-868) The authors suggest in this that they have come close to isolating exactly how the parasite causes harm on the molecular level.

In sequencing E. histolytica not only can we learn more about a major parasite infecting humans, but they suggest this information might lead to new chemotherapeutic agents. Also, by having a sequenced genome, we can compare it more closely with other parasites (such as the two listed above) to learn more about why it is so harmful to humans. The main purpose of this research as a whole is to learn how it works to find a better way to treat and prevent infection.

 I chose this article because we all have some background on E.hystolitica so we can relate more to the research they are conducting. Also, although an obvious choice of a parasite, the article itself was well written and more understandable having some knowledge of the parasite. Many of the other articles I looked at were very vague, just describing an experiment, not discussing any results. This article discussed the impact their research has on science as well as why they were doing what they were doing.

¹http://journals.cambridge.org/fulltext_content/ERM/ERM4_09/S1462399402004453sup001.pdf

Loftus, Brendan et al., “The genome of the protest parasite Entamoeba histolytica.” Nature. 0028-0836. Volume 433. Issue 7028. 2005. p865-868, September 20, 2012.  http://www.nature.com/nature/journal/v433/n7028/full/nature03291.html

Eimeria elephantuli : A new coccidian parasite found in the rufous elephant shrew.

The species Eimeria elephantuli is the first coccidian parasite that has been found in the rufous elephant shrew, Elephantulus rufenscens (Modrý, Jirků, Hůrková, 2005). Coccidian parasites are single-celled organisms and need an animal cell to live and reproduce in. Other species in the subclass of coccidia can be found in pets such as dogs, and infect animals through consumption of contaminated soil or feces. Coccidiosis is dangerous for puppies because it may cause bloody diarrhea and death if left untreated (CAPC 2012).

The rufous elephant shrew is an insectivore that can grow up to 60g, and is generally located in East Africa south of the Sahara (Modrý, Jirků, Hůrková, 2005). The new species, E. elephantuli, was found in the feces and the intestines of three of the six elephant shrews that were examined. The parasites present in the intestines were in stages of gametogony, which means they were working on forming gametes, with large numbers of oocysts, which contain the parasite’s zygote, being located in the feces of the infected subject animals, indicating that the oocysts are likely the infective stage of the parasite (Modrý, Jirků, Hůrková, 2005).

                So far, only two species of Eimeria have been discovered and reported from insectivores in Africa, but the two differ greatly in general appearance and can be told apart easily by these differences. E. elephantuli is easy to distinguinsh from the other species of Eimeria because of the characteristics of the oocysts, including size, morphology, and the shape of intracellular bodies (Modrý, Jirků, Hůrková, 2005). Further research is needed to know where E. eufenscens picks up the infection though it is likely it eats infected prey.

CAPC. [Internet]. 2012 [Cited 2012 Sept 19]. Pets and Parasites. Available from http://www.petsandparasites.org/

Modrý, D., Jirků, M., Hůrková, L. 2005. A new coccidian parasite (Apicomplexa: Eimeriidae) from the rufous elephant shrew, Elephantus rufescens, from Kenya. African Zoology. 40: 327-329.

Description of Leishmania equatorensis Sp. N. (Kinetoplastida: Trypanosomatidae), A New Parasite Infecting Arboreal Mammals in Ecuador

In Ecuador in 1982, two unidentified parasites were isolated from a squirrel and a sloth in a humid tropical forest. However, few studies were done to fully identify them until Grimald et al. (1992) began their research. After extensive testing, the unidentified parasites were determined to belong to the Leishmania braziliensis complex and were named Leishmania equatorensis (Grimald et al. 1992). Leishmania equatorensis is very similar to Leishmania braziliensis with the exception of only a couple different enzymes found while running an enzyme electrophoresis test. Otherwise, they are undistinguishable to physical appearance and behavior.

Leishmania equatorensis is found in the liver and spleen of its host. Leishmania equatorensis grows at a slower rate than other Leishmania species and has a lower intensity of parasites in the lesions. Hamsters were used for this study due to their nature of being very susceptible to Leishmania infections. The hamsters showed swelling without ulceration within one to three months after being infected.

At the time of this article’s publication, Leishmania equatorensis had only been isolated from small mammals, but this does not mean that the new strain of Leishmania isn’t a threat. Six different kinds of Leishmania have been isolated from human patients in Ecuador and cutaneous and mucocutaneous Leishmania are endemic there. Not enough research has been done on Leishmania equatorensis to confidently say that it cannot use humans as hosts. Leishmania equatorensis also has the same life cycle as other Leishmania and so it can be a valuable parasite for studying other Leishmania species.

Citation

G. Gabriel Jr., R. Kreutzer, Y. Hashiguchi, E. Gomez, T. Mimory, R. Tesh, 1992, Description of Leishmania equatorensis Sp. N. (Kinetoplastida: Trypanosomatidae), A New Parasite Infecting Arboreal Mammals in Ecuador, Mem. Inst. Oswaldo Cruz, 87(2): 221-228

 

-Kaitlin Smith (Revised 10/11/12)

Detection of the Signature of Natural Selection in Humans: Evidence from the Duffy Blood Group LocusMartha T. Hamblin & Anna Di Rien
　
Resistance to the parasite Plasmodium vivax (causes Malaria) due to the reduced occurance of the "Duffy" surface antigen regoin in red blood cells in many Sub-Sarahan Areas causes a natural selection gradient for many African Americans. The Duffy blood group has three main alleles,(which are the alleles needed for inorder to become infected with Malaria) FY*A, FY*B, FY*O are at the highest frequency in Asia and Pacific Areas, intermediate in the Europeans and Americans, while it is at its lowest frequency in the Sub-Saharan ares resulting in increased resistance to Malaria. It is thought that there has been a huge positive impact of natural selection othese particular groups of alleles. 　

Individuals that are homozygous for the FY*O allele are completely immune to Malaria because Plasmodium vivax can only bind onto the Duffy blood group, which is located on the surface of red blood cells. It is said that the sub-saharan populations have aquired a FY*O homozygous mutation, which has resulted in Africans being Immune from Malaria. Directional natural selection has been the cause for this recent trend in the genetic resistance to Malaria in Africans. 　

The Duffy allele frequency variations of five populations in sub-saharan African were observed as well as 17 individuals from Italy. PCR (Polymerase Chain Reactions) were performed on all genomes inorder to analyze the sequence variation of the FY*A, FY*B, FY*O alleles. A two-step PCR process was used to analyze the Duffy Gene region and the FY*O variation in Africans compared to Europeans. it was found that all of the Africans being studied were homozygous for the FY*O allele while the 17 Italians only carried the FY*A & FY*B alleles. 　

Inconclusion, there is ample evidence to show that there has been directional selection being acted upon the Duffy gene regoin which further makes African more resistance to Malaria than other ethnicities. is is unsure if Plasmodium vivax pure existance is the cause of the FY*O fixation in Africans but it definitely a prominent factor.　
Shana Alderman
Literature Cited:
1. Hamblin, M.,T.Rien, A.,D. 2000. Detection of the signature of natural selection in humans: evidence from the duffy blood group locus. Science Direct. 66 (5): 1669–1679.