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Part I of the clinical trials for a human hookworm vaccine candidate, which began in late 2011, concluded with promising safety results. The vaccine candidate will now begin Part II of the study, according to a Sabin Vaccine Institute press release Nov. 5.Part I of the study, which took place in Belo Horizonte, Brazil, included vaccinating healthy adults with vaccine candidate Na-GST-1 who have never been exposed to the parasitic roundworm and observe them for health and safety issues.The next stage of Phase I clinical trial will include vaccinating 66 healthy, hookworm-exposed adults in hookworm endemic Americaninhas, Brazil.The volunteers, ages 18-45, will receive three shots over a four month period and monitored for the vaccine’s safety and volunteer immune response.“Eventually, a human hookworm vaccine will be used to protect children at risk of infection. Because the hookworm-exposed population being vaccinated in Part II of this trial is representative of the eventual target population, we’re closer to making this goal a reality,” said Dr. David Diemert, the trial’s principal investigator.Dr. Peter Hotez, president of the Sabin Vaccine Institute said, “A human hookworm vaccine will help more than 600 million people worldwide who currently suffer from the infection.”According to the release, the trial is being conducted in partnership with a team based at the Oswaldo Cruz Foundation (FIOCRUZ) of the Brazilian Ministry of Health, a member of the Sabin Vaccine Institute Product Development Partnership (Sabin PDP).Hookworm is the second most common intestinal roundworm in humans worldwide, only behind Ascaris lumbricoides, with an estimated half a billion people infected at any one time.There are two species that are human pathogens; Ancylostoma duodenale which is found in Africa, India, Europe and China, and Necator americanus, which is found in the Americas. However, many areas are endemic for both species.Hookworm disease caused by N. americanus is the prevailing species in the southeastern United States.You get hookworm in areas of unsanitary conditions where people defecate on the ground and the climate is favorable. Warm, moist climates and sandy soil are the environments hookworms thrive in. Infective larvae can survive up to a month in the soil under ideal conditions.Hookworm is not an issue in cold climates because the larvae cannot survive.People get infected by walking barefoot over contaminated soil where the hookworm larvae can penetrate the skin. It is a particular problem in farmers in developing nations worldwide. Also, small children get it by sitting bare-butt on the ground that has hookworm.Ancylostoma duodenale may also be acquired orally, transmammary and transplacentally.After the larvae penetrate the skin, it is carried in the bloodstream to the heart and then the lungs. Here they climb the windpipe and are swallowed to the intestines where they mature to adults.In the intestines, the adults attach and suck blood. The blood loss can be significant depending on the amount of worms present. A. duodenale drinks more blood per worm (0.2-0.3 ml) per day thanN. americanus (0.03 ml), and are therefore more pathogenic.The symptoms you may see depends on what stage of infection the person is in. During invasion when the larvae initially penetrate the skin, there may be a severe allergic reaction known as “ground itch”.While the larvae are migrating through the lungs, an infected person may experience a mild pneumonia with a cough.When adults are in the intestines, symptoms may include diarrhea, pain, and nausea.In very heavy infections, blood loss can reach 100 ml per day, resulting in iron deficiency anemia and weakness due to blood loss.In addition, protein deficiencies, enlarged liver and spleen (“pot-bellied children”) and developmental disorders like mental, physical and sexual may occur in severe hookworm disease.For more infectious disease news and information, visit and “like” the Infectious Disease News Facebook page
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