Some travel-related infections are not widely known, leaving patients vulnerable

WINTER WEATHER AND school breaks will send many travelers off to warmer locations for relaxing vacations. Most travelers are aware of infectious diseases like malaria, West Nile virus, chikungunya, and Zika virus that are carried by mosquitoes. They use bug spray and avoid areas with too great a risk of contracting one of these illnesses. However, tourists are generally unconcerned about walking barefoot on beaches and swimming in unfamiliar water, leaving them open to a host of other unpleasant travel-related diagnoses they will carry back home. Health care providers can educate patients before travel about taking precautions and, by asking for a detailed travel history, can accurately diagnose and treat patients who come in with illnesses not frequently seen in the US.

Not all beachgoers are as aware of the consequences of sand flea infestation as Marlene Thielecke, a PhD student in tropical medicine, who was living in Madagascar in 2011  when a sand flea invaded the sole of her right foot. She knew how to extract the flea, but she decided to let it continue its life cycle in her foot, observing it for several months. She discovered that it didn’t expel eggs as expected, as it had not been fertilized. If she kept her foot covered, it couldn’t come in contact with a male flea. Her findings were published in 2013. “To the people who really have it, one is a joke. One is nothing. There are very many people really suffering from this,” she said. “My experiment is a very small spot in this big disease.”³

Tungiasis is a parasitic infestation of the fertilized female sand flea Tunga penetrans. Most frequently found in Central and South America, the Caribbean, India, and sub-Saharan Africa, the sand flea targets bare feet, often in sand or shady areas near rotting vegetation. Living in or visiting areas with slum conditions and close proximity to domestic animals can also be risk factors.¹ Once inside the bare foot, the sand flea feeds on blood and begins to grow with her eggs, eventually releasing them into the human host.¹ Within 24 hours, patients may notice papules on their toes or feet that feel tender. Within 2-3 days, patients will experience severe itching and irritation.² Lesions may cause pain when walking.

Vacationers who spend time in the ocean may come in contact with the larvae of the thimble jellyfish, Linuche unguiculata, that cause seabather’s eruption. The jellyfish are often referred to as “sea lice” (they are not true sea lice, which are skin parasites of fish and are not harmful to humans). The larval jellyfish are large enough to be seen by the naked eye, but when they’re the water, they are nearly invisible. They get caught inside swimwear and sting, likely triggered by the pressure of being squeezed between swimwear and the body.⁴ Patients notice a papular rash from minutes to days after leaving the seawater, which lasts for 5-7 days. The rash is accompanied by itching. Some patients, usually children, also develop systemic symptoms like fever, headache, malaise, and vomiting.⁵ Swimmers under 16 and those who spend prolonged periods in the water, like surfers and snorkelers, are most at risk.⁶

A similar reaction, cercarial dermatitis, also called swimmer’s itch, can happen to saltwater or freshwater swimmers who come in contact with cercaria (larval stage) of bird schistosomes (parasites) that find their way into intermediate hosts like snails and subsequently into humans. Cercarial dermatitis is an allergic reaction to the cercaria entering the outermost layer of the skin, where they usually die quickly. The pruritic rash usually appears on skin not covered by a bathing suit. A first exposure may result in only a mild reaction, while subsequent exposures may increase the severity of the reaction.⁷ Lifeguard Leslie Ritter uses her sensitivity to the parasites to test the water in Crystal Lake in Michigan by taking a 30-minute dip before starting swimming lessons. “If her skin starts to tingle, she knows something in the lake is after her — and swimming lessons are canceled.”⁸ Ritter records her reaction along with wind and temperature data and sends the results to the Michigan Swimmer’s Itch Partnership. “There are days when I can feel those little buggers grabbing me right when I am coming out of the water,” she says.⁸

“Adventure travelers, Peace Corps volunteers, missionaries, soldiers, and ecotourists” are at increased risk of schistosomiasis infection, according to the US Centers for Disease Control and Prevention (CDC).⁹ Schistosomiasis is caused by blood flukes that come in contact with humans in freshwater. A rash often appears within a few days of exposure and then clears. Then, over several weeks, the patient will experience systemic symptoms of an allergic reaction, including “urticaria[l], fever, sweats, chills, cough, and headache.”¹⁰ Symptoms may also include enlarged lymph nodes and enlarged liver and spleen as the adult parasites begin to lay eggs. If the acute form of schistosomiasis is not treated, it can become chronic and last for years, causing damage to organs and the central nervous system.¹⁰

Considered a Neglected Tropical Disease (NTD), schistosomiasis is found in much of Africa, China and Southeast Asia, the Caribbean and eastern South America, and the Middle East.⁹ In 2016, more than 206 million people worldwide had been diagnosed with schistosomiasis. In January 2018, a clinical trial for a schistosomiasis vaccine in Brazil was announced. “Right now, people are treated for schistosomiasis only to be rapidly reinfected. Creating a vaccine is critical to stopping this cycle,” said Dr. Dr. David Diemert, principal investigator and associate professor of microbiology, immunology, and tropical medicine at the George Washington University School of Medicine and Health Sciences.¹¹

US infections of strongyloidiasis occur primarily in “immigrants, refugees, and military veterans”¹² who live for a period of time in areas known to be home to Strongyloides stercoralis, a gastrointestinal helminth (parasitic worm). They are found primarily in the southeastern US, and worldwide in tropical climates. The helminth usually penetrates a lower extremity.

A patient’s infection may lay dormant for years. As in the case of Angeline, a 32-year-old administrative assistant in Canada who immigrated from Haiti, the infection may manifest once a patient’s immune system is compromised. “Strongyloidiasis is a sleeping disease,” said Angeline’s doctor, Anne McCarthy, MD, an infectious disease specialist. “It can exist in your body and do relatively little harm until you give it an advantage.”¹³

Whether symptoms manifest quickly or years later, they can include “erythematous, serpiginous rased lesion(s), up to 15 cm in length, most commonly located on the buttock, torso, and thighs (generally speaking, within 12 inches of the anus).”¹⁴ The lesions are often associated with pruritus, whether or not the parasite is visible. Other symptoms include abdominal pain, nausea, constipation or diarrhea, and coughing or wheezing.¹⁴

Travelers and people living in endemic areas for long periods of time, like members of the Armed Forces, can take steps to prevent infection:

• Be aware of what diagnoses are endemic to the area where you are planning to travel.
• Shower immediately after swimming in seawater or freshwater with the bathing suit removed.⁴
• Wear shoes and protective clothing on lower extremities, especially when walking on sand or soil.¹
• Make sure the water supply you use for bathing is clean and safe.¹⁵
• There is evidence that vigorously rubbing the skin with a towel after swimming or bathing in areas where schistosomiasis is endemic can prevent the parasite from invading the skin.¹⁵

These easy-to-follow guidelines can prevent some unpleasant and possibly dangerous infestations from accompanying travelers back home. Just a little more awareness can help any adventurer have a great vacation.

References

1. Chen CW, Thong HY, Jee SH. Tungiasis: a case report and review of literature. Dermatologica Sinica. 2011. https://doi.org/10.1016/j.dsi.2011.01.004. Accessed February 9, 2018.

2. Lederman E, Craft N. Tungiasis. In: Goldsmith L, editor. VisualDx Visual Clinical Support Tool [online]. Rochester, NY: Logical Images; 2018. https://www.visualdx.com/visualdx/diagnosis/tungiasis?moduleId=18&diagnosisId=52451. Accessed February 9, 2018.

3. Khazan, O. The Researcher who let a sand flea live in her foot. The Atlantic. 2013. https://www.theatlantic.com/health/archive/2013/11/the-researcher-who-let-a-sand-flea-live-in-her-foot/281599/. Accessed February 9, 2018.

4. Rossetto AL, Dellatorre G, da Silveira FL, et al. Seabather’s eruption: a clinical and epidemiological study of 38 cases in Santa Catarina State, Brazil. SciELO. 2009. http://dx.doi.org/10.1590/S0036-46652009000300008. Accessed February 9, 2018.

5. Norris R, Feldman, J. Seabather’s eruption. In: Goldsmith L, editor. VisualDx Visual Clinical Support Tool [online]. Rochester, NY: Logical Images; 2018. https://www.visualdx.com/visualdx/diagnosis/seabathers eruption?moduleId=101&diagnosisId=52315. Accessed February 9, 2018.

6. Kumar S, Hlady WG, Malecki JM. Risk factors for seabather’s eruption: a prospective cohort study. Public Health Rep. 1997;112(1): 59-62. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1381840/pdf/pubhealthrep00042-0061.pdf. Accessed February 9, 2018.

7. Norris R, Feldman, J. Cercarial dermatitis. In: Goldsmith L, editor. VisualDx Visual Clinical Support Tool [online]. Rochester, NY: Logical Images; 2018. https://www.visualdx.com/visualdx/diagnosis/cercarial dermatitis?moduleId=42&diagnosisId=52363. Accessed February 9, 2018.

8. Mitic, GB. Creepy swimmer’s itch parasite in northern lakes can scratch summer fun. Scientific American. 2017. https://www.scientificamerican.com/article/creepy-swimmer-rsquo-s-itch-parasite-in-northern-lakes-can-scratch-summer-fun/. Accessed February 9, 2018.

9. Montgomery, S. Schistosomiasis. Centers for Disease Control and Prevention Yellow Book. 2017. https://wwwnc.cdc.gov/travel/yellowbook/2018/infectious-diseases-related-to-travel/schistosomiasis. Accessed February 9, 2018.

10. Lederman E, Craft N. Schistosomiasis. In: Goldsmith L, editor. VisualDx Visual Clinical Support Tool [online]. Rochester, NY: Logical Images; 2018. https://www.visualdx.com/visualdx/diagnosis/schistosomiasis?moduleId=101&diagnosisId=52303. Accessed February 9, 2018.

11. Hackett DW. Schistosoma vaccine candidate enters phase Ib clinical trial. Precision Vaccinations. http://www.precisionvaccinations.com/schistosomiasis-also-known-snail-fever-or-bilharzia-caused-parasitic-flatworms-africa-and-latin. Accessed February 9, 2018.

12. Abanyie, F. Strongyloidiasis. Centers for Disease Control and Prevention Yellow Book. 2017. https://wwwnc.cdc.gov/travel/yellowbook/2018/infectious-diseases-related-to-travel/strongyloidiasis. Accessed February 9, 2018.

13. Loney S. She was fighting cancer – but her treatment triggered a completely different disease. Reader’s Digest. 2017. https://www.rd.com/health/conditions/strongyloides-parasite/. Accessed February 9, 2018.

14. Lederman E, Craft N. Strongyloidiasis. In: Goldsmith L, editor. VisualDx Visual Clinical Support Tool [online]. Rochester, NY: Logical Images; 2018. https://www.visualdx.com/visualdx/diagnosis/strongyloidiasis?moduleId=101&diagnosisId=53534. Accessed February 9, 2018.

15. Clerinx J, Van Gompel A. Schistosomiasis in travellers and migrants. Travel Medicine and Infectious Disease. 2011;9(1): 6-24. http://www.travelmedicinejournal.com/article/S1477-8939(10)00189-4/fulltext. Accessed February 9, 2018.