Buruli ulcer is a bacterial infection of the skin that can cause serious swelling, lesions, and permanent deformity. Much of the epidemiology, transmission, and control of the disease remain unknown.
Chagas disease, also called American trypanosomiasis, is a parasitic disease that is transmitted by infected reduviid bugs (also called triatomine, assassin, or kissing bugs). Humans contract the disease when the infected feces of the insect vector enter the body, typically by scratching the insect bite. Although Chagas disease first causes an acute infection, the majority of mortality and morbidity caused by Chagas are the result of organ damage from chronic infection.
Cholera is an acute bacterial infection of the intestine that is transmitted through contaminated water. The bacteria cause severe watery diarrhea, known as “rice water” diarrhea, and vomiting. Fluid loss can lead to severe dehydration and death within 24 hours of the onset of symptoms if dehydration is not treated.
Dengue fever (DF) is a viral disease transmitted by infected mosquitoes. DF causes severe, flu-like symptoms with high fever and extreme muscle and joint pain. Dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) are less common but more severe forms of the disease. DHF/DSS initially presents with very similar symptoms to DF. The disease then progresses to a stage where the blood vessels become permeable, or “leaky,” causing a breakdown of the circulatory system, fluid loss, and possibly death.
Diarrheal diseases are a collection of diseases caused by multiple viral, bacterial, and parasitic organisms that share the common symptom of diarrhea, defined as the passage of three or more loose or liquid stools per day. The diarrheal diseases cholera, ETEC, rotavirus, shigellosis, and typhoid are also profiled separately, but we have grouped them together with other forms of infectious diarrhea in this profile to discuss general diarrhea treatments. Irrespective of the underlying cause of the diarrhea symptoms, diarrheal diseases can lead to severe dehydration or even death when left untreated.
Dracunculiasis, or Guinea worm disease, is caused by infection with a parasitic roundworm known as a Guinea worm. The disease manifests as painful and disfiguring sores. Guinea worm disease is considered to be in the late stages of global eradication.
ETEC are bacteria that colonize the small intestine and cause severe diarrhea, dysentery, abdominal cramps, and fever. ETEC can be life threatening due to significant fluid loss and severe dehydration. Beyond its burden in endemic countries, ETEC is the leading cause of diarrhea in travelers from developed regions returning from vacation in low resource countries.
Fascioliasis is caused by a parasitic flat worm that primarily affects the liver and bile duct. The parasite is transmitted by consumption ofFasciola spp. cysts on plants from contaminated fresh water. Chronic infection with fascioliasis can result in pain, abdominal inflammation and the formation of scar tissue and fibrosis in the bile duct, but it is not fatal.
Human African Trypanosomiasis (HAT), also called African sleeping sickness, is a parasitic disease that is transmitted by infected tsetse flies. HAT can occur as a chronic or acute infection depending on the sub-species of parasite responsible for the infection. In either case, the disease progresses through two distinct stages. Stage 1 is the initial stage of infection and presents with non-specific symptoms including fever, rash, and fatigue. Untreated stage 1 HAT results in stage 2 disease where parasites invade the central nervous system causing severe neurological symptoms and eventually death. The symptoms resulting from central nervous system invasion include personality changes, mental deterioration, increased sleep, and eventually coma. The term “sleeping sickness” arose from the observation that patients with this disease become progressively sleepy until they eventually fail to wake up.
Human immunodeficiency virus (HIV) is a retrovirus that causes acquired immune deficiency syndrome (AIDS), a disease characterized by progressive deterioration of the immune system. The diminished immune function of HIV/AIDS patients puts them at risk for opportunistic infections, which may lead to death.
Leishmaniasis is a widespread parasitic disease transmitted by the bite of an infected sandfly. The disease occurs in three forms, cutaneous leishmaniasis, mucocutaneous leishmaniasis, and visceral leishmaniasis, each of which varies in incidence and severity. The three predominant forms of leishmaniasis can affect the skin, mucosa, and/or internal organs resulting in severe disfigurement, disability, or death.
Leprosy, also known as Hansen’s disease, is a bacterial infection of the tissue of the skin, peripheral nervous system, mucosa, and upper respiratory tract that can cause skin lesions and serious deformity. There is an ongoing attempt to eliminate leprosy as a public health problem.
Lymphatic filariasis (LF) is caused by a group of parasitic worms that are transmitted through the bites of infected mosquitoes. Although the majority of people infected with these parasites are asymptomatic, slow damage to the lymphatic system and other organs from chronic infection leads to a variety of pathologies. The most well recognized manifestation of LF is elephantiasis.
Malaria is a parasitic disease that is transmitted by infected mosquitoes. The non-specific nature of the symptoms of uncomplicated malaria, including fever, chills, sweating, body aches, nausea, headache, vomiting, and diarrhea, make clinical diagnosis challenging. When left untreated, uncomplicated malaria can rapidly progress to severe disease, especially in young children.
Onchocerciasis is a skin and eye disease caused by the parasitic worm, Onchocerca volvulus. The infection is spread by blackflies that breed in fast-flowing water, giving it the common name “river blindness.” Onchocerciasis is the second leading cause of infectious blindness worldwide. Although there is no vaccine available to prevent O. volvulus infection, aggressive vector control and drug delivery programs have dramatically decreased disease incidence over the past thirty years.
Pneumococcal disease is a collection of maladies caused by the bacterium Streptococcus pneumoniae. The infection commonly manifests as pneumonia, meningitis, sepsis, and middle ear infections. In the developing world, S. pneumoniae is a significant cause of death in infants while in the developed world the elderly and immunocompromised are at highest risk.
Rotavirus gastroenteritis is a viral infection predominantly affecting infants and young children that causes severe diarrhea, vomiting, and fever. Because of the rapid dehydration that results from the combination of diarrhea and vomiting, the disease can be fatal.
Schistosomiasis (also known as bilharzia), is a disease caused by a parasitic worm that primarily lives in the blood. The parasite is transmitted to humans by penetration of the skin in fresh water. The majority of morbidity and mortality associated with schistosomiasis is the result of slow damage to the host organs caused by accumulation of parasite eggs in the tissues over many years.
Shigellosis is an infection by bacteria of the genus Shigella that causes severe abdominal symptoms, including diarrhea, dysentery, abdominal cramps, fever, and rectal pain. Shigellosis can result in death. The disease is more dangerous than other gut pathogens because it can penetrate the lining of the intestine and cause severe inflammation of the intestine and systemic complications.
Hookworm is a parasitic roundworm of the small intestine that is transmitted through the soil. Although most patients are asymptomatic, heavy worm burdens lead to anemia, diarrhea, abdominal pain, weight loss and loss of appetite. While hookworm is associated with a relatively small number of deaths, chronic anemia caused by the disease is associated with significant morbidity.
Trachoma is a bacterial infection of the eye transmitted by close person-to-person contact. With frequent and repeated infections, trachoma infection can lead to permanent visual impairment.
Soil-transmitted helminths are a family of intestinal worms that include the organisms that cause ascariasis, hookworm (profiled separately), and trichuriasis. Ascariasis and trichuriasis are transmitted through ingestion of parasite eggs in contaminated soil. While ascariasis and trichuriasis are associated with a relatively small number of deaths, they can result in intestinal symptoms, weakness, and malnutrition which, over time, can impact childhood development and adult productivity.
Tuberculosis (TB) is a bacterial disease that most commonly affects the lungs (pulmonary TB). In otherwise healthy individuals, most infections are latent and therefore asymptomatic. About 5% of people infected with TB will develop active disease within the first year after exposure and an additional 5% are likely to develop active TB from latent infection over the course of their lifetime.
Typhoid fever, or enteric fever, is a bacterial infection caused by Salmonella enterica subspecies enterica serovar Typhi (abbreviated Salmonella Typhi). The disease is spread by ingestion of contaminated food or water. Typhoid commonly presents with a sudden onset of fever, headache, abdominal pain, and diarrhea and can quickly progress to a variety of potentially fatal complications, including gastrointestinal hemorrhage, intestinal perforation, and neurological dullness or delirium.
Yaws is a chronic bacterial infection that primarily affects skin, bone, and cartilage. The disease is disfiguring and ultimately debilitating. However, yaws is considered to be in the late stages of global elimination.