Travelers should avoid walking barefoot in the tropics, especially near rural villages or beaches where sanitation measures are lacking. In these areas, hookworm (Ancylostoma/Necator) may be endemic. It is estimated that over 900 million people worldwide are infected.

The eggs of the parasite are deposited in the soil after human defecation. After a couple of days, the eggs hatch into infective larvae that remain viable in the soil for several weeks. They burrow into exposed skin (usually the feet) resulting in localized itching, redness and swelling (‘ground itch’). They then migrate from the skin, into the blood, lungs then ultimately mature in the intestines where they feed on blood. Most hookworm infections are without symptoms. However, in large numbers, they can cause severe anemia, growth retardation, shortness of breath and generalized weakness. Hookworm disease can be treated with several safe and effective medications including pyrantel pamoate or mebendazole.

Other skin-burrowing parasites in tropical soils include strongyloidiasis and cutaneous larva migrans (creeping eruption). Cutaneous larva migrans is prevalent throughout the tropics and is caused by larvae of the dog and cat hookworms. Moist sandy soil (e.g. beaches, children’s sand piles) contaminated by dog a cat feces is a common site of infection.

Finding the eggs in a stool specimen can make diagnosis.

The best means of protection against these parasites is by wearing shoes when walking in endemic areas and avoiding direct skin to soil contact.

MELIOIDSIS

Melioidosis is a mysterious, tropical soil disease of humans and animals caused by the bacteria Pseudomonas pseudomallei. The disease has been reported throughout the tropics, but is endemic primarily in Southeast Asia. The bacteria, is a saprophyte which grows in wet soil, ponds and rice paddies. The disease was first described by a British pathologist working in Burma in 1911. For many years, it was dismissed as an uncommon illness, until hundreds of American soldiers became very ill from it during the Vietnam War. The rural poor are most likely to be exposed to melioidosis as a result of their close contact with soil and water. Since they are the least likely to have access to sophisticated medical care, it is probable that active clinical melioidosis is under diagnosed in many countries.

Melioidosis is primarily contracted by soil contamination of skin wounds and abrasions. Less common routes include ingestion and inhalation. The disease is not thought to be contagious and person-to-person transmission is rare.

The symptoms of the disease are variable and can mimic many other illnesses. Occasionally, the disease is not recognized until the victim is critically ill. Lung infection is the most common presentation. However, the disease may occur in the blood (septicaemia), as well as many organs, including the skin, brain, lungs, heart, liver, bones, joints and even the eyes. Victims can also have insidious or dormant infections that only become symptomatic many years from the time of exposure.

Diagnosis of the infection is usually made by laboratory culture of the organism. Antibody levels can be measured in blood test.

Melioidosis is resistant to many antibiotics. Milder forms of the disease such as those involving the skin can be drained or surgically excised. However, relapse of the infection, even years later is frequent. Severe cases such as those involving the lungs or blood (septicaemia) are often fatal.

There is no vaccine against melioidosis. Therefore, wounds and abrasions that are contaminated by soil in endemic regions should be thoroughly cleaned and washed with soap and water, after which an antiseptic cream should be applied and the wound bandaged. All deep or infected wounds should be treated by a doctor.