Correct!
1. Ivermectin
The patient is infected with Strongyloides stercoralis, a roundworm commonly known as the thread worm. In conditions of immunodeficiency the worm may disseminate causing a potentially fatal Strongyloides hyperinfection syndrome (SHS) (1). Ivermectin is the drug of choice (2). Thiobendazole is an alternative but less effective. Praziquantel is used to treat tapeworm infections. Piperacillin and tazobactam (Zosyn®) is an antibacterial and has no activity against parasites.
The cycle of Strongyloides is given in Figure 4.
Figure 4. Life cycle of Strongyloides.
Strongyloides larvae exist in a free-living form in contaminated soil and infects humans via skin penetration through shoeless feet. Cutaneous penetration by the parasite produces characteristic skin lesions, called "larva currens". After penetrating the skin the larvae gain access to the venous circulation and are carried to the lungs; then penetrates the alveolar wall. They are then able to migrate to the glottis, where they are swallowed, allowing the nematode access into the gastrointestinal tract, where it resides in the small bowel. The larvae then burrowed into the mucosa and transform into adults and produce eggs. The eggs develop into rhabditiform larvae which are released into the gastrointestinal tract where they can live for decades. However, in the immunocompromised host the rhabditiform larvae are capable of reinfecting its host by invading the bowel wall or perianal skin (3). As in our patient, acceleration of the life cycle, by autoinfection where the rhabditiform larvae within the host resulting Strongyloides hyperinfection syndrome (SHS).
Strongyloides can be quiescent for many years in an infected host who travel to the United States from endemic areas. Since Strongyloides is rare in the United States, often times diagnosis is not made pre-mortem. Perhaps the largest population at risk is that of patients receiving immunosuppressive therapy for another disease, especially those whose cases are managed with glucocorticoids. As our case illustrates, steroid therapy and its associated suppression of cell-mediated immunity can remove the controls from controlled infection with S. stercoralis and resulting in dissemination. While patients from endemic areas are at obvious risk, there is also a risk to those who travel to endemic areas, including veterans of military service (3).
Our patient was chronically immunosuppressed by steroid therapy which accelerated Strongyloides through autoinfection causing dissemination. Because of the severity of her illness she was treated with both ivermectin and thiobendazole. Survival of disseminated strongyloidiasis is possible, and early diagnosis and treatment improve outcome. Mortality of disseminated strongyloidiasis remains at 43%; it climbs to 77% with the loss of immune function. Death is frequently the result of either secondary infectious or respiratory failure (3,4). This patient was from Mexico where Strongyloides is endemic and asking "whose your momma" might give a clue to this difficult diagnosis.References