Whole genome sequencing of multiple Leishmania donovani clinical isolates provides insights into population structure and mechanisms of drug resistance

Leishmania species are protozoan parasites that are transmitted by a bite from a sandfly. These parasites are found in 88 countries and infect an estimated 12 million people worldwide. Genome sequencing of certain Leishmania species has been, but not on Leishmania donovani even though it is considered the most important Leishmania species in public health. Attempts to eliminate L. donovani from India have become a more difficult task due to drug resistant strains of L. donovani emerging. This study done by Downing et al. (2011) was performed to better understand L. donovani genome to enhance public health intervention strategies.

A high-quality draft of Leishmania donovani genome was created based off of isolates of             L. donovani collected from 17 infected patients. The reference genome was used to map out natural variation data. After generating the genome sequences for each of the 17 parasite sample, genome-wide single-nucleotide polymorphisms (SNPs) and structural variation (SV) were revealed and genes with differential patterns in antimonial resistant and susceptible samples were recognized. The variation of SNPs was limited in parasite strains that were antimonial resistant (Downing et al. 2011).

This study showed that there is a correlation between genome-wide single-nucleotide polymorphisms and drug-resistant strains of Leishmania donovani. More sensitive and powerful approaches to observing genomic diversity should be performed in order to further research L. donovani and other Leishmania species’ drug resistance and how genomes are correlated (Downing et al. 2011).

This article relates to the study by Guevara et al. (1994) “Presence of Leishmania braziliensis in blood samples from cured patients or at different stages of immunotherapy” because Guevara et al (1994) studied the presence of a Leishmania species in humans after being treated for the infection and Downing et al. (2011) researched how drug resistance in Leishmania species is correlated with genome.

Citation

T. Downing, H. Imamura, S. Decuypere, T. Clark, G. Coombs, J. Cotton, J. Hilley, S. Doncker, I. Maes, J. Mottram, M. Quail, S. Rijal, M. Sanders, G. Schonian, O. Stark, S. Sundar, M. Vanaerschot, C. Hertz-Fowler, J. Dujardin, M. Berriman, 2011, Whole genome sequencing of multiple Leishmania donovani clinical isolates provides insights into population structure and mechanisms of drug resistance, Genome Research, 21: 2143-2156

-Kaitlin Smith

Babesia microti:This Parasite Bites

Babesia microti is a parasite transmitted to humans by a tick bite. Babesia microti can only be transmitted from human to human by blood transfusion. The primary way to diagnose the parasite is using an immunofluorescence assay and test for specific antibodies in the blood (Johnson et al., 2009). This is a significantly effective way to test for Babesia microti. It is the primary cause of human Babesiosis in the United States with an increase in fear for blood transfusions with B. microti within them. In this study the food and drug administration, have worked to overcome the transfusion-transmitted Babesia microti (Johnson et al., 2009).

This article discussed the best way to diagnose Babesia microti. From these diagnoses they were able to locate the most highly dense areas in the Northeastern United States in 2000 through 2007. Most of the parasite infected ticks were found in Connecticut and Massachusetts. Babesia microti itself is a fairly newly discovered parasite. The first U.S. reported case of Babesia microti was reported in 1969 in Nantucket Island in Massachusetts. B. microti is only transmitted through blood transfusions and can be tested by blood, so data for these results were taken from the American Red Cross (Johnson et al., 2009).

After a positive test result for Babesia microti from blood donors, the American Red Cross collected routine samples of blood  to test for Immunoglobulin (IG) G antibodies. Using the diagnostic technique of the immunofluorescence assay test, the researchers were able to determine whether the positive donors have the Immunoglobulin G antibodies (Johnson et al., 2009). The presence of certain Immunoglobulin antibodies in the blood provides a measure of exposure for Babesia microti. If a donor is positive for the Immunoglobulin M antibodies it is thought of to be a lower risk infection. If a donor is positive for the Immunoglobulin G antibodies the donor is thought to be at a much higher risk of infection because the infection is longer living and can be chronically infected with the parasite (Johnson et al., 2009).

I found this article interesting because I was personally diagnosed with Babesia microti within the past month. As a regular blood donor, I was contacted after my donation, notified that I had the infection and was told I needed to be treated. As in the article, with not much information about the parasite and still further research being conducted, I was asked to participate in their study. I am now scheduled to donate vials of blood ever few weeks to the American Red Cross to test for the presence of certain Immunoglobulin antibodies in my blood. This first verifies if I am still infected with it, and second will verify how infected I am with it. With immunofluorescence assay testing, we have come along was to be able to test for parasites like these.

Literature Cited

Johnson, S.T., Cable, R.G., Tonnetti, L., Spencer, B., Rios, J., Leiby, D.A. 2009. Seroprevalence of Babesia microti in blood donors from Babesia-endemic areas of the northeastern United States:2000 through 2007. Transfusion. 49(12): 2574-2582

Babesia microti

           The lifecycle of Babesia microti is fairly simple. It is epidemiologically found worldwide wherever ticks with that parasite can be found. There are about 99 species of Babesia so geographically they can be found all over. Various species of ticks are found over the world transmitting B. microti to different hosts. In the United Kingdom, Ixodes trianguliceps is the species of tick that transmits Babesia. Ixodes dammini for example is the tick found in the Northeast United States (Boustani et al., 1996). The lifecycle of I. dammini lasts approximately two years.

            The larval form of the definitive host, I. dammani is produced in the spring when the eggs hatch. The larva feed throughout August and September on a variety of hosts. These hosts contract the babesial infection from the larva. The most common host of Ixodes dammini is the white-footed mouse, Peromyscus leucopus (Boustani et al., 1996). P. leucopus is accounting for 90% of the vector host animals on Nantucket Island, where the first U.S. reported case of Babesia microti was reported is 1969 (Johnson et al., 2009). Other animals such as chipmunks, mice, rabbits, voles, and deer are also common hosts.

            When the Ixodes dammini takes a blood meal from any of its hosts it injects spoorozoites which undergo asexual reproduction and budding in the host. The humans enter the lifecycle by being bitten by an infected tick. Similarly to the animal hosts, when I. dammini takes a blood meal it injects spoorozoites into the human, also undergoing asexual reproduction and budding. Humans are usually the dead end hosts. Babesia microti can only be transmitted from human to human by contaminated blood transfusions (Johnson et al., 2009).

 Babesia is transmitted from the larval phase of the tick to the nymph phase of the tick. The disease acquired by humans is from the nymph phase, rarely the adult phase. The nymph stage is the size of a single poppy seed and is extremely difficult to see even when looking for. The adult phase is host specific usually to white-tailed deer, Odocoileus virginianus (Boustani et al., 1996). The tick lifecycle is complete after depositing the eggs and the death of the tick.

Literature Cited

Boustani, M.R., Gelfand, J.A. 1996. Babesiosis. Clinical Infectious Diseases. 22(4): 611-614

Johnson, S.T., Cable, R.G., Tonnetti, L., Spencer, B., Rios, J., Leiby, D.A. 2009. Seroprevalence of Babesia microti in blood donors from Babesia-endemic areas of the northeastern United States:2000 through 2007. Transfusion. 49(12): 2574-2582

Comparative morphology of human and animal malaria parasites

Comparative morphology of human and animal malaria parasites

U.  Mackenstedt, C. Brockelman, H. Mehlhorn and W. Raether

                Special fixations and standardized methods were used to compare human and animal malaria parasites Plasmodium falciparum, P. malariae, P. vivax, P. berghei, P. gallinaceum to compare morphological traits. Parasitized host cell walls  were essentially observed as well as morphological alterations to the host erythrocytes such as knobs, invaginations, and caveola- vesicle complexes on cell membrane surfaces ( Mackenstedt et  al. 1989)

            Blood from infected patients and animals were analyzed using transmission microscopy. K₃Fe(CN)₆ was added to the blood- osmium solution to emphasize the membrane transformation. All Plasmodium spp. species, displayed significant alterations to the parasitized erythrocytes that are not seen in infected ones. Specifically P. vivax exhibited micro vesicles with a limited cellular membrane of 40-60nm. Parasitized erythrocytes that were in their last stage of differentiation contained numerous clefts that densely filled the cytoplasm                       (Mackenstedt et al. 1989).

            Numerous caveola-vesicle complexes found in P. vivax are shown to be responsible for Schuffners dots on infected erythrocytes. Present ultra-structural studies have concluded that P. vivax is the only species that demonstrates stippling (Schuffners dots) due to numerous small vesicles in the cytoplasm(Mackenstedt et al. 1989). Examining the species- specific morphological alterations to infected erythrocytes induced by infections of P. vivax morphologies of Plasmodium species will further broaden our knowledge on the behavior of malaria species as well as aid in the discovery of better treatment for the devastating infection.

1.      U., Mackenstedt, C.,  Brockelman, H.,  Mehlhorn & W.,  Raether. 1989. Comparative morphology of human and animal malaria parasites. Parasitol Res. 75:528-535.

Is Dracunculiasis on the Verge of Extermination?

The feasibility of eradicating dracunucliasis has already been discussed for multiple decades. Serious efforts to stop the disease have been going on since the late 80s (Aylward, 2005). Due to the life cycle of worms in the Dracunculus genus, eradication would be possible if certain steps were taken to reduce the spread of the disease. Since Dracunculus medinensis is known to only infect humans, control efforts would not need to focus on possible reservoir hosts in the environment. Since the disease is widespread, control of other animal species would be expensive and not feasible in many of the areas, so without worry of reservoir hosts, the disease can be more easily eradicated. Treatment of drinking water or clean water sources would be required to avoid the disease. This may be too expensive in some communities where a well cannot be built or water cannot be easily treated before use. Water sources could also be treated to destroy any copepods which may be hosting larvae, though this would not be feasible on a large scale. Programs aimed at educating people about the disease would be possible, such as teaching them how to avoid it or prevent the spread of the parasites. Control efforts such as these have already resulted in a decrease in the number of infections. In the early 90s, the number of infected individuals was estimated at 3 million, instead of over 10 million as it had been a decade earlier (Selby, 1992). Commitment of local governments to build concrete lined wells and make drinking water filters available has been important to the efforts.

Aylward, R.B.  Birmingham, M. 2005. Eradicating Pathogens: The Human Story. British Medical Journal, Vol. 331, No. 7527. 1261-1262.

Selby, P. 1992. Dracunculiasis: The End of the Worm. British Medical Journal.

 Vol. 304, No. 6836. 1205.

Plasma Ascorbic Acid Levels in Lambs with Coccidiosis

Coccidiosis is caused by single-celled parasites and most commonly affects lambs that are between 2 and 8 weeks of age. Most sheep herds are infected with coccidiosis, but only some lambs develop clinical coccidiosis, which causes symptoms such as dullness, lack of appetite, diarrhea, dehydration, weight loss, rectal prolapse, and anemia (Şahinduran et al. 2006). It has also been found that sheep with coccidial infections had low concentrations of ascorbic acid, and a deficiency of ascorbic acid can cause diarrhea and pneumonia (Şahinduran et al. 2006).

A farm in Burdur province was used to obtain 30 lambs between 1 and 2 months old, where 20 lambs were infected with coccidian oocysts, and 10 lambs were kept healthy. Before starting the study all lambs were classified as healthy according to their blood composition, body temperature, and respiratory rate. Fecal samples from the lambs in the healthy (control) group were examined and determined to be free of coccidians (Şahinduran et al. 2006).

The lambs in the infected group developed symptoms of clinical coccidiosis, with several severe cases of anemia. Lambs with severe symptoms were found to have more than one species of Eimeria in their system, with the most common species found being Eimeria bakuensis and Eimeria ovinoidalis (Şahinduran et al. 2006). When compared to the control group, the infected group had a significant difference in ascorbic acid levels, with the infected group having ascorbic acid levels of 0.78 ± 0.19 mg/dl while the healthy group had levels of 2.00 ± 0.58 mg/dl of ascorbic acid (Şahinduran et al. 2006).

The ascorbic acid levels in the infected sheep decreased due to lack of appetite and the accompanying decrease in the intake of proteins, leading to immune system depression. Depression of the immune system often leads to impaired resistance to other infectious organisms (Şahinduran et al. 2006). Infected lambs also had increased levels of leukocytes caused by tissue damage in the intestine and the accompanying fever (Şahinduran et al. 2006). Because of the low levels of vitamin C in lambs with coccidiosis, vitamin C in combination with classical treatments is recommended as a useful treatment plan for individuals in the herd with clinical coccidiosis (Şahinduran et al. 2006).

Reference

Şahinduran, Ş., Sezer, K., Büyükoğlu, T., Yukari, B., Albay, M. 2006. Plasma ascorbic acid levels in lambs with coccidiosis. Turkish Journal of Veterinary & Animal Sciences. 30: 219-221.

Can a malaria and helminth co-infection increase the chance of anemia?

          Nkuo-Akenji and her colleges investigated the prevalence of anemia in individual infected with intestinal helminthes and Plasmodium farcipirum, or both. The aim was to identify if a coinfection was connected to anemia, and to determine the significant predictors of anemia in the community. Since some parasitic infections together could cause modifications of the specific immune response to each pathogen, there could also be a modification of the clinical expression of each infection (anemia). Children in endemic regions are the most heavily afflicted group (of all 3 illnesses) so the study was done on 425 children under age 14 in Bolifarriba, Cameroon.

            Intestinal helminthes refers to the group of parasitic worms which reside in the latter part of the human digestive system, absorbing nutrients from our diet through their skin. The parasite Plasmodium farcipirum causes Malaria, a disease known to be one of the number one causes of death in underdeveloped tropic areas.

            Blood samples were taken by finger pricks and then stained on a slide, where intensity of malaria parasitemia was counted (severe was >5000/microliter of blood). Packed cell volumes (% of red blood cells in blood) were found to determine if the sample was anemic (normal = 40%, anemic <31%). The quantification of helminthes was done using the Kato-Katz technique on stool samples (egg counts >90th percentile defined heavy infection).

The results demonstrate that high infections of either parasite are likely to lead to high coinfections. Coinfections however, are not more likely to be correlated with anemia. Anemia prevalence increased significantly with high P. falciparum parasite loads, more specifically; children infected exclusively with P. falciparum recorded the highest prevalence of anemia. Their results show that malaria, fever and age can be used as predictors of anemia.

MALARIA AND HELMINTH CO-INFECTION IN CHILDREN LIVING IN A MALARIA ENDEMIC

SETTING OF MOUNT CAMEROON AND PREDICTORS OF ANEMIA

Theresa K. Nkuo-Akenji, Primus C. Chi, Jerome F. Cho, Kenneth K. J. Ndamukong, and Irene Sumbele

Department of Medical Laboratory Science, Faculty of Health Sciences, University of Buea, South West Province, Cameroon.

Babesia microti Treatments

             In a previous post I discussed the importance of studying Babesia microti.  One of the reasons is that it has the same vector, Ixodid ticks, as the parasite Borrelia burgdorferi, which causes Lyme disease.  Ten percent of patients, in the United States, infected with Borrelia burgdorferi are also co-infected with Babesia microti (Shoemaker et al., 2006).  The number of individuals with co-infections is still on the rise.  The double infection of the two parasites can cause more severe and persistent symptoms.  Patients with co-infections showed resistance to the drugs Azithromycin and Atovaquone, which are normally used to treat these parasitic infections (Shoemaker et al., 2006).  Other problems with the previous drugs of choice were that it did not relieve post Lyme disease syndrome (PLS) symptoms.  PLS is a set of symptoms that arise after Lyme disease has been treated.  It is most likely due to a neurotoxin released by the parasite B. burgdorferi.  It is believed that Babesia microti may also release a similar neurotoxin (Shoemaker et al., 2006).                                   

            An experiment was preformed in order to find the most effective drug for treating co-infections of B. microti and B. burgdorferi.  The results showed that a treatment of atovaquone  plus cholestyramine over a 9-week period is necessary to relieve the symptoms of both infections (Shoemaker et al., 2006).  The drug cholestyramine was also effective in relieving PLS symptoms in majority of the patients.  This is most likely due to the ability of cholestyramine to bind to the neurotoxins secreted by B. burgdorferi.  Once cholestyramine binds to the neurotoxin it can be excreted through the feces.  The reason previous drugs were less effective at relieving PSD symptoms is because although they would kill the parasites B. microti and B. burgdorferi they would leave the neurotoxins in the host’s blood stream (Shoemaker et al., 2006).  

            The reason I chose this article was because in my previous article I discussed methods of detecting Babesia microti.   I wanted to write a post about treatments for those who have been infected with the disease.  In my first blog post I also talked about how individuals can often be infected by Babesia microti and Borrelia burgdorferi at the same time.  This article discussed effective methods of individuals who have been co-infected with both parasites.  Since there has been an increase in the number of cases were the two parasites are being transmitted together, it is beneficial to have a drug that responds to both. 

References

Shoemaker, R.C., Hudnell, K.H., House, D.D., Kempen, A.D., Pakes, G.E. 2006.      Atovaquone    

          Plus Cholestrymine in Patients Coinfected With Babesia microti and Borrelia burgdorferi       

          Refractory to Other Treatment. Advances in Therapy.23 (1):1-11