A 66-year-old man presents with chronic leg swelling. He is a recent immigrant from Fiji. He reports episodes of fever and headache. Physical exam reveals thick, scaly skin on both legs with swelling extending to the genitals. Swollen inguinal lymph nodes are palpable. What was the likely vector of transmission for his infection?
Flea
Body Louse
Mite
Mosquito
Tick
Correct answer
Mosquito
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correct answer: D
This man exhibits the signs and symptoms of elephantiasis, a condition caused by the nematodes Wuchereria bancrofti and Brugia malayi. They are both spread by the bite of an infected mosquito (choice D). The lymphatics are infected, resulting in chronic leg and genital swelling. Wuchereria infection is endemic to the Pacific Islands, much of Africa, whereas Brugia is found in the Malay Peninsula and much of Southeast Asia. Importantly, mosquitos are vectors for many other bacteria species, which you should be familiar with.
Fleas (A) may serve as vectors for the transmission of Yersinia pestis (bubonic plague) between rodents and humans. Murine typhus (endemic typhus) fever, and in some cases Hymenolepiasis (tapeworm) can also be transmitted by fleas.
Body Lice (B) serve as vectors for Rickettsia prowazekii, causing Epidemic typhus, Bartonella quintana (trench fever causing endocarditis commonly among the homeless), and Borrelia recurrentis (a recurrent fever found in east Africa).
Mites © bites may cause otitis or dermatitis and can act as vectors for Serratia marcescens or Staphylococcus intermedius/Staphylococcus chromogens.
The tick (E) can act as a vector for Borrelia Burgdorferi or Coxiella-like species. Most famously, tick bites carrying Borrelia are the cause of Lyme Disease.