Visit the World Health Organization web site. Look up the current status of Ebola and Leishmaniasis, and compare them to a disease (of your choice) that occurs closer to where you live (consult Figure 8.6 in your text for information).
What organisms cause the three diseases? What is their current distribution and prevalence? What environmental (think of natural environment, not their home environment) and social factors (that affect the environment) contribute to their spread? Does any treatment exist for the diseases?
FIGURE 8.6 Start dates of some recent outbreaks of highly lethal infectious diseases. Why are super-contagious organisms emerging in so many different places?
Source: Data from U.S. Centers for Disease Control and Prevention
The largest recent death toll from an emergent disease is for HIV/AIDS. Although virtually unknown 35 years ago, acquired immune-deficiency syndrome is estimated to have killed at least 34 million people so far. The WHO estimates that 37 million people are now infected with HIV, but that half of them are unaware of their condition. Because of improved treatment, the number of deaths is declining, to 1.5 million or fewer per year. Although two-thirds of all current HIV infections are now in sub-Saharan Africa, the disease is spreading rapidly in South and East Asia. However, a greater focus on this disease has brought progress. New infection rates have fallen by 50 percent or more in 25 countries—13 of them in sub-Saharan Africa. Half of all the reductions in HIV infections in the past two years have been among children.
Still, the costs of this disease are terrible. As chapter 7 points out, without AIDS the life expectancy in Swaziland would be about 65 years. With AIDS, the average life expectancy is now only about 33 years. Worldwide more than 14 million children—the equivalent of all children under age five in America—have lost one or both parents to AIDS. The economic costs of treating patients and lost productivity from premature deaths resulting from this disease are estimated to be at least $35 billion per year, or about one-tenth of the total GDP of sub-Saharan Africa.
Emerging diseases devastate wildlife populations
Humans aren’t the only ones to suffer from new and devastating diseases. Domestic animals and wildlife also experience sudden and widespread epidemics. When new diseases spread among wildlife, they are sometimes called ecological diseases. A particularly devastating example has been destroying bat populations across North America in the past decade. In 2006, people living near a cave west of Albany, New York, reported something peculiar: Little brown bats (Myotis lucifugus) were flying outside during daylight in the middle of the winter. Inspection of the cave by the wildlife management officers found numerous dead bats near the cave mouth. Most had white fuzz on their faces and wings, a condition that is now known as white-nose syndrome (WNS). Little brown bats are tiny creatures, about the size of your thumb. They depend on about 2 grams of stored fat to get through the winter. Hibernation is essential to making their energy resources last. Being awakened just once can cost a bat a month’s worth of fat.
The white fuzz has now been identified as filamentous fungus (Geomyces destructans), which thrives in the cool, moist conditions where bats hibernate. We don’t know where the fungus came from, but, true to its name, the pathogen is highly destructive. Occurring in only a few states a decade ago, the disease has now been found in almost every state and province in eastern North America. Biologists estimate that nearly 6 million bats already have died from this disease. It isn’t known how the pathogen spreads. Perhaps it moves from animal to animal through physical contact. It’s also possible that humans introduce fungal spores on their shoes and clothing when they go from one cave to another.
In some areas, bat populations have fallen by 95 percent or more. So far, seven species of bat are known to be susceptible to this plague, and it has been detected in five additional species. Some researchers fear that bats could be extinct in 20 years in the eastern United States. Losing these important species, which consume insects and pollinate plants, would have devastating ecological consequences.
An even more widespread and lethal epidemic is currently sweeping through amphibians worldwide. A disease called Chytrid fungus (or Chytridiomycosis) is causing dramatic losses or even extinctions of frogs and toads throughout the world (fig. 8.7). A fungus called Batrachochytrium dendrobatidis causes the disease. It was first recognized in 1993 in dead and dying frogs in Queensland, Australia, and now seems to be spreading rapidly, perhaps because the fungus has become more virulent or amphibians are more susceptible due to environmental change. Most of the world’s approximately 6,000 amphibian species appear to be susceptible to the disease, and around 2,000 species have declined or become extinct in their native habitats as part of this global epidemic. African clawed frogs (Xenopus sp.), which are resistant to fungal infections and thus may be carriers of the disease, are a possible vector for this disease. Widespread use of these frogs for research and pregnancy testing may have contributed to the rapid spread of the pathogen.
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Leishmaniasis, Ebola and Aids Diseases
Certainly, Leishmaniasis disease is caused by protozoan Leishmania parasites mostly found and transmitted by female phlebotomine sandflies. On the other hand, Ebola disease is caused by Ebola virus mostly found in wild animals, and can be transmitted through contact with blood, secretions, organs and body fluids among others. Lastly, AIDs disease is caused by a virus known as human immunodeficiency virus (HIV). It is transmitted through exchange of body fluids with an infected person such as breast milk, blood, vaginal secretions and semen.
Current Distribution and Prevalence of the Diseases
Based on 2015, statistics, at most 1million cases of Leishmaniasis disease which are new took place per year worldwide, which came along with at most 30,000 deaths annually. Furthermore, current state of Ebola disease has been diminishing within West Africa where the outbreak took place between years 2014-2016. In 24th July 2018, one of the most affected region, Democratic Republic of Congo, officially ended the ninth outbreak of the disease. Lastly, since 2017, the widespread of AIDS has been increasing with 1.8 million new cases being reported that year.
Environmental And Social Factors Causes Of The Diseases
Environmental factor which contribute to Leishmaniasis disease transmission include living in rural areas with temperatures ranging 15-38 °C and with humidity of at least 70% . Social factors include interaction with animals mostly cattle and flies, which mostly takes place in agricultural areas. Furthermore, Environmental factor that leads to transmission of Ebola virus include forests and wildlife areas inhabited by wild animals. Social factors that lead to the spread of the disease include interaction with wild animals and infected people: mostly through sexual contact. Lastly, Environmental factor that leads to spread of AIDs include areas with high rate of social evils such as prostitution and rape. Social factors include having sexual interaction with infected people without any means of protection such in prostitution and raping.
Treatment of the Diseases
Treatment of Leishmaniasis disease is based on several factors such as the type of the disease, geographical area and the parasite species. Mostly the disease is treated through immunocompetent system since medicines cannot fully get rid of the parasite responsible. Contrarily, there is no scientific confirmed treatment of Ebola disease. However, certain measures have always been kept into consideration to improve survival such as care-rehydration with oral fluids and specific syndromes treatment. Lastly, AIDs cannot be treated but its virus can only be suppressed through particular medical measures such as intake of ARV drugs. The drugs control replication of the virus in human body, which allows the body immune system