, , , spp, , ,
Skin lesions are a common problem in the tropics and they could be a primary problem or secondary to an underlying systemic condition. It is important to focus on infections that are treatable, transmissible, and have a high morbidity or mortality. The history must include details of previous travel, previous skin lesions, activities indulged in, immune status of the host, vaccinations, and prophylaxis. Exposures to fresh or sea water, animals, arthropods, plants, breaks in skin including tattoos, sexual activities, and medications are important. Time of onset of skin lesions, their evolution, and associated symptoms, such as itching, pain, or fevers, are important clues to the diagnosis. Although tropics are often considered exotic locations skin problems can often be from cosmopolitan causes. Sunburn, scabies, and prickly heat are common and chronic skin problems, such as atopic dermatitis, may exacerbate in a tropical environment. Tropical biodiversity also results in a wide variety of plants and hence hypersensitivity to plants, plant products, and drugs may also occur. It is important not to forget mundane causes, such as pyoderma and folliculitis. Because skin manifestations are myriad a syndromic approach does help to narrow down a definite diagnosis ( Table 4 ).
Dermatologic syndromes and etiology
Syndrome | Important Points | Differential Diagnoses |
---|---|---|
Fever with rash | Duration of fever, associated symptoms, type and pattern of rash, exposure to sick contacts, mosquitoes, geographic area | Dengue fever, chikungunya, measles, rubella, mumps, typhoid, Katayama fever |
Migratory rashes | Exposures, travel, and eosinophilia | Cutaneous larva migrans, gnathostomiasis, Larva currens |
Fever with papules | Systemic symptoms, immunocompromise | Histoplasmosis, penicilliosis, nocardiosis, coccidiodomycosis, paracoccidiodomycosis |
Nodules | Geographic locale, occupation, exposures | Myiasis, onchocercomas, cutaneous leishmaniasis |
Vascular nodules | Immune status, exposure to brackish water and sandfly bites | Rhinosporidiosis, chronic bartonellosis |
Ulcers, cutaneous and mucosal | Vaccination and nutrition status, exposures to cattle or pets, occupation, proximity to the jungle | Buruli ulcer, cutaneous leishmaniasis, cutaneous diphtheria, tropical ulcer, atypical mycobacteria, paracoccidiodomycosis, sporotrichosis |
Eschars | Insect bites painful or painless, surrounding induration, exposures, systemic symptoms | Scrub typhus, anthrax, spider bite, trypanosomiasis, plague, tularemia, African tick typhus |
Nodules with sinuses | Occupation, trauma, color of grains | Mycetoma, actinomycetoma, botryomycosis |
Diarrhea as a syndrome in the tropics has been described as “Montezuma’s revenge” and “Delhi belly” because of the associated morbidity. It also is the second most important cause of child deaths younger than the age of 5 years contributing to almost 500,000. In the Global Burden of Disease Study 9 diarrhea was a leading cause of death among all ages contributing to 1.31 million deaths. Most of the deaths in children and adults were attributable to Rotavirus , Shigella spp, and Salmonella spp. However, deaths on the whole have been reduced by 20.8% from 2005 to 2015. In the Global Enteric Multicenter Study 10 done in children younger than age 5, interventions to reduce deaths should be directed against five pathogens: stable enterotoxigenic E coli , enteropathogenic E coli , Cryptosporidium spp, Rotavirus , and Shigella spp. Different clinical syndromes of diarrhea have been defined, each reflecting different etiology and pathogenesis. These are briefly described in Tables 5 and and6 6 .
Etiologic classification of diarrhea based on stool appearance
Stool Appearance | Small Bowel | Large Bowel |
---|---|---|
Appearance and volume | Watery and large volume | Mucoid or bloody and small volume |
pH and reducing substance | <5.5 and positive for reducing substances | >5.5 and negative for reducing substances |
Serum and stool WBC | No bandemia and WBCs in stool <5/hpf | Bandemia and WBCs in stool >10/hpf |
Organisms | , , , , adenovirus | (EIEC, EHEC), , , , , , |
Abbreviations: EHEC, Enterohaemorrhagic E coli ; EIEC, Enteroinvasive E coli ; hpf, high-powered field; WBC, white blood count.
Etiologic classification based on symptomatology
Symptoms and Signs | Pathophysiology | Possible Etiology |
---|---|---|
Large watery stools | Secretory small bowel | ETEC, EPEC, , |
Large volume watery | Enterotoxin mediated | , ETEC, spp |
Many small volume stools | Large bowel irritation | , , , , , |
Tenesmus, fecal urgency, dysentery | Colitis | , EIEC, EHEC, , , , |
Diarrhea and vomiting | Toxin-mediated gastroenteritis | , , , |
Fever and diarrhea | Mucosal invasion | , EHEC, EIEC, , , , , |
Persistent diarrhea | Secondary malabsorption, invasion | , , , , , |
Abbreviations: EHEC, Enterohaemorrhagic E coli ; EIEC, Enteroinvasive E coli ; EPEC, Enteropathogenic E coli ; ETEC, Enterotoxigenic E coli .
Various challenges exist in the diagnosis of tropical infections. The challenges are multiple and are divided as discussed next.
The burden of disease and the kind of setting where the disease is being diagnosed often determines the need of an appropriate diagnostic test. In a high-prevalence, low-resource setting a test that is low cost, point of care, requiring little technical expertise, with a high positive predictive value is required. In contrast in a low-prevalence, low-resource setting, additional tests may need to be performed to confirm the diagnosis. Subclinical and asymptomatic manifestations of a tropical disease may also make it difficult for a diagnostic test to distinguish between clinical disease and the former. In addition, if a test is serology-based in an endemic setting it may be difficult to establish causality for the clinical manifestations of the disease if baseline antibody titers is high.
Although there are obvious infrastructural and financial challenges in low-resource settings there are also impediments with the lack of trained laboratory staff and quality assurance of available laboratory diagnostics. In addition, an ideal laboratory test needs to be rapid, point of care, requiring minimal technical expertise, following norms of good clinical laboratory practice and health and safety measures in the workplace. The advent of molecular techniques has made this a reality and the need of the hour is an accurate rapid diagnostic test. Today the high burden diseases, such as tuberculosis, HIV infection, and malaria, all have rapid diagnostic tests, which has been a revolution with regard to appropriate case management of these diseases. A definite challenge has been to find similar easy diagnostic test strategies for diagnosis and epidemiologic surveillance for other tropical infections associated with high morbidity and mortality.
The WHO constitution dictates, “All people share the right to the highest attainable standard of health.” Huge advances are being made toward internationally agreed global health targets, some of which include a reduction in child mortality by 50% between 1990 and 2013 and a 48% decline in AIDS related deaths since the peak of the HIV/AIDS epidemic in 2005 with at least half the infected people being able to access antiretroviral therapy. Many international agencies, such as the WHO and UNAID (Joint United Nations Programme on HIV/AIDS), pharmaceutical companies and Combating Antibiotic Resistant Bacteria Biopharmaceutical Accelerator and the Global Antibiotic Research and Development Partnership have incessantly campaigned for increased access to medicines leading to an achievement of many of the health-related millennium development goals. 11
Controlling, eliminating, and eradicating neglected tropical diseases has been a major focus for the WHO since 2003 as it moved away from specific diseases to the health needs of poor communities. Over the years many disease conditions that were believed to require a concerted effort by the WHO were included. These were identified as follows ( Table 7 ) 12
List of neglected tropical diseases – WHO 2017
Dengue | Rabies | Trachoma | Buruli ulcer |
Yaws | Leprosy | Chagas disease | Echinococcosis |
Human African trypanosomiasis | Cysticercosis | Schistosomiasis | |
Soil-transmitted helminths | Foodborne trematodiasis | Onchocerciasis | |
Lymphatic filariasis | Snakebite envenoming | Mycetoma | |
Chromoblastomycosis and other deep mycoses | Scabies |
This has led the WHO to adopt five major strategies to combat these diseases:
Tropical medicine is an amalgamation of infectious and noninfectious diseases and deals with many important issues, such as water, hygiene, and sanitation, which is out of reach for many low- and middle-income tropical countries. As a result, the health indices for these countries often suffer necessitating global and local public health interventions. Research, development, global support, and funding along with access to major health interventions has empowered many of these countries to overcome the challenges faced by them while combating tropical diseases.
The author has no financial conflicts of interests to declare and did not receive any funding to complete this article.
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Research and Reports in Tropical Medicine is an international, peer-reviewed, open access, online journal. The journal publishes original research, case reports, editorials, reviews and commentaries on all areas of medicine and disease in tropical regions.
Research and Reports in Tropical Medicine is an international, peer-reviewed, open access, online journal publishing original research, case reports, editorials, reviews and commentaries on all areas of Tropical Medicine.
Research and Reports in Tropical Medicine is an international, peer-reviewed, open access, online journal. The journal publishes original research, case reports, editorials, reviews and commentaries on all areas of medicine and disease in tropical regions.
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