Anthrax (Any temperate or tropical rural area where animal husbandry is common): Anthrax is a gram positive spore-forming aerobic rod (Bacillus anthracis) cutaneous or pulmonary infection. Cutaneous anthrax is characterized by a dark centered erythematous papule surrounded by edematous and vesicular tissue. The papule enlarges, ulcerates, forms eschar, which later sloughs. Lymphadenopathy, fever, malaise, headache, and nausea and vomiting may also occur. After the eschar sloughs, hematogenous spread and sepsis may occur, with resulting shock, collapse, and hemorrhagic meningitis. Pulmonary anthrax (a concern with respect to biological warfare) is characterized by fever, malaise, headache, respiratory congestion, and pneumonia or mediastinitis. Anthrax is treated with penicillin G or tetracycline. Mortality is high, especially in pulmonary anthrax.
Bartonellosis (Oroya fever) (South America/Andes Mountains): Bartonellosis is a gram negative bacterial systemic infection with Bartonella bacilliformis, which is transmitted by sandflies. Infection is characterized by insidious onset of fever, malaise, headache, myalgia; or in other cases, acute onset high fever, chills, drenching sweats, lymphadenopathy, hemolytic anemia, liver involvement and altered consciousness. Essential features are fever, progressive hemolytic anemia, generalized lymphadenopathy, and exposure to sandflies. Salmonellosis is a common complication of bartonellosis. Nodular (and often ulcerated) lesions occur one to three months after the onset of illness. Treatment is with penicillin, tetracycline, streptomycin, or chloramphenicol.
Filariasis: See full discussion (Distribution given below). The filarial parasites are tissue-dwelling roundworms whose microfilarial (mf) larvae are transmitted by several species of mosquitos or flies. The most problematic forms of filariasis are (1) Bancroftian filariasis and Malayan filariasis (much of the tropical and subtropical world between the Tropics of Cancer and Capricorn) which involve the lymphatic system and result in elephantiasisis; (2) loiasis or loa loa (tropical Africa) in which worms live in subcutaneous tissue; and (3) Onchocerciasis (tropical Africa and to a lesser extent Central and South America) which causes river blindness and skin disorders. Treatment in most cases is effective only against the mf, hence the infection continues and repeated treatment (with ivermectin and/or DEC) may be necessary.
Melioidosis (Southeast Asia): Melioidosis is infection by Pseudomonas pseudomallei (gram negative bacillus) with symptoms of fever, pulmonary infection that may range from bronchitis to necrotizing pneumonia. Acute septicemic melioidosis is most common among debilitated persons. Focal suppuration (nodule, lymphangitis, lymphadenopathy) results from inoculation through a break in the skin. Chronic suppurative disease may involve virtually any body system. Recrudescence may occur many years after the initial infection. Treatment is according to susceptibility. Common antibiotics used are TMP-SMX (not in Thailand), Augmentin, doxycycline, and cephalosporins.
Pinta (mal de pinto, carate) (Rural areas of Latin America): Pinta is a spirochetal (Treponema carateum) skin infection characterized by a painless scaling papule with regional lymphadenopathy progressing to non-ulcerating maculopapular erythematous areas. Spread is by extension and by secondary lesions (pintides), which may be numerous. Pintides may be psoriatic or circinate in configuration. Initially the pintides are red, then slate blue, and then loss of pigmentation occurs, resulting first in brown areas, and eventually in mottled white skin. Lesions appear in various stages of development and are seen most commonly on the extremities and face. Pinta is decreasing in incidence and prevalence. The preferred treatment is 2.4 million units of IM benzathine penicillin G for adults and 1.2 million units for children.
Plague (Worldwide, but primarily rural and lightly populated areas in undeveloped countries): Plague is an acute febrile zoonotic disease caused by Yersinia pestis, a microaerophilic coccobacillus of the family Enterobacteriaceae. Plague is transmitted primarily by flea (from rodents) bite, but also from direct inoculation through handling infected mammal carcasses or via the respiratory route from infected droplets from a patient with pneumonic plague. The most recent pandemic was in the late 19th and early 20th centuries and resulted in estimated 12,000,000 deaths. In recent years (1970s-1990s), most cases have been reported in Africa, Asia, and the Americas. There are three common forms of plague: bubonic (most common), pneumonic (most rapid and most frequently fatal), and septicemic - with the latter two either primary or secondary to metastatic spread. Plague is manifested by abrupt onset of high fever, severe headache, severe myalgias, prostration, and in some cases, delirium. The incubation period is 2-10 days. An ulcer may develop at the inoculation site. Lymphadenitis is followed by painful, draining bubo(s). Pneumonic plague produces fulminant pneumonitis with frothy bloody sputum and sepsis. Hematogenous spread or septicemic plague is characterized by rapid decline, coma, and purpura - hence the term "black plague." Treatment must be quickly instituted in all cases. IM streptomycin is the first line treatment, though IM or IV gentamicin is frequently used. IV or po tetracycline or doxycycline are also used.
Schistosomiasis or Bilharzia: See full discussion (Numerous areas of the world, especially Africa and Asia with variants and locations noted in the full discussion). Schistosomiasis is caused by Schistosoma sp. and encompasses several syndromes, not all of which are evident in all infected persons. Initial symptoms may include a pruritic, papular rash - most commonly in persons who do not live in endemic areas. Acute schistosomiasis (Katayama fever) occurs in primary infection 1-2 months after exposure to heavy parasite loads. Symptoms may include fever of several weeks duration, headache, urticaria, cough, hepatosplenomegaly, lymphadenopathy, diarrhea, and eosinophilia. Hematuria and dysuria occur in some infections. Symptoms tend to gradually diminish over several months, but may intensify as more eggs are deposited. Chronic hepatosplenic schistosomiasis is a consequence of eggs retained in tissue and prolonged infection - usually > 10 years duration. The liver may be large or small and firm with nodularity. Portal hypertension, splenomegaly, or esophageal or gastric varices may occur. Hematemesis and splenomegaly are common presenting symptoms, with normal liver function. Periportal fibrosis and portal hypertension is associated with glomerulonephritis (proteinuria, renal failure) and pulmonary hypertension (cor pulmonale). Granulomatous tissue in the bowel results in bloody diarrhea. The last (chronic) stage varies according to species, with some species primarily affecting the liver and intestines, and one species affecting primarily the urinary tract. In general, patients with chronic schistosomiasis tend to present in developed countries with lethargy, colicky abdominal pain, mucoid/bloody diarrhea, or dysuria and hematuria. Salmonella infection concurrent with schistosomiasis is common and is resistant to treatment unless the schistosomiasis is also treated. Complications include progression of liver, kidney, or other organ dysfunction for many years after transmission has been interrupted - especially with heavy infection and re-exposure. Central nervous system lesions occur, but rarely. Treatment is according to species: For S. haematobium and S. mansoni, praziquantel 20/kg po bid for one day; for S. japonica and S. mekongi, praziquantel 20/kg po tid for one day are the treatments of choice. S. mansoni may also be treated with oxamniquine in a single po dose (with food) of 15 mg/kg. S. haematobium in North and East Africa may be treated with metrifonate 7.5-10 mg/kg every other week for a total of 3 doses.
Sporotrichosis (Worldwide): Sporotrichosis is a mycotic infection from inoculation of tissue with Sporothrix schenckii mold via an open wound - often associated with gardening activities. Sporotrichosis occurs in several forms, including (1) plaque sporotrichosis - a non-tender maculopapular granuloma at the site of inoculation; (2) lymphangitic sporotrichosis - a papule at the site of inoculation, followed by draining nodules along proximal lymphatic channels; (3) osteoarticular sporotrichosis - polyarticular arthritis that develops slowly and may include draining sinuses at joints. Treatment for plaque sporotrichosis is with potassium iodide or itraconazole. Treatment for lymphangitic or osteoarticular sporotrichosis is with a prolonged course of itraconazole and only about 50% of patients are cured.
Trypanosomiasis (African) or African sleeping sickness (Tropical Africa): Trypanosomiasis is caused by protozoal parasites, Trypanosoma brucei rhodesiene or T b gambiense, transmitted by bite of the tsetse fly. T b rhodesiene infections are more virulent than T b gambiense; and in the former, patients experience three stages of illness (trypanosomal chancre, hemolymphatic, and meningoencephalitic) as opposed to two stages in the latter (trypanosomal chancre and meningoencephalitic) with significantly milder symptoms. The painful trypanosomal chancre (3-10 cm) appears about two days after the bite and lasts 2-4 weeks. The hemolymphatic stage is characterized by high fevers lasting several days, with symptom-free periods of days to weeks. Less common manifestations of this stage are severe headache, malaise, arthralgia, lymphadenopathy, circinate rash, pruritis, and hepatosplenomegaly. Weight loss and debilitation also occur, and myocarditis may develop. The meningoencephalitic stage is characterized by progressive apathy, nighttime insomnia and daytime somnolence, anorexia, retarded speech, extrapyramidal signs (tremors, fasciculations, choreiform movements, and Parkinsonian-like appearance), and finally, coma and death. Treatment is complex and toxic, and depends on the infecting organism and stage of illness. Among the medications currently in use are suramin, melarsoprol, pentamidine, eflornithine, and corticosteroids.