Biweekly Prophylactic Doxycycline for Travelers' Diarrhea

Abstract

A double-blind study to determine the efficacy of biweekly oral doxycycline in the prevention of travelers' diarrhea was conducted among 46 Peace Corps volunteers during their first six weeks in Honduras. The volunteers took either 100 mg of doxycycline per dose or a placebo for three weeks and were observed for an additional three weeks. There was no significant difference in the number of persons with travelers' diarrhea in the two groups (eight of 24 in the doxycycline group and 10 of 22 in the placebo group) in the three weeks when the drug was taken. However, significantly fewer episodes (P less than 0.05) of travelers' diarrhea occurred in the doxycycline group than in the placebo group at the end of the second, third, and fourth weeks. Enterotoxigenic Escherichia coli (ETEC) was the most common pathogen identified. ETEC from 13 (62%) of 21 stool samples were resistant to doxycycline. Biweekly doxycycline was only marginally effective in preventing travelers' diarrhea and did not prevent diarrhea secondary to doxycycline-resistant ETEC.

Lack of emergence of resistant fecal flora during successful prophylaxis of traveler's diarrhea with norfloxacin

“…The 88% rate of protection afforded by norfloxacin compares favorably with rates of 59 to 95% afforded by other antibiotics studied previously in controlled trials (4,6,(14)(15)(16)(17). The lowest rate, 68%, occurred in the group of Peace Corps volunteers taking doxycycline in areas where doxycycline resistance had been documented (16).…”

Travelers’ Diarrhea, New Perspectives

“…The highes rates have ap peared in Peace Corps volunteers, presum ably because of their more primitive living conditions [3,[8][9][10], This is also suggested in the study by Steffen et al [6] of travelers' diarrhea in 16,568 European tourists; those taking 'adventure tours' had the highest rate of diarrhea. Sex and season of travel are not factors in diarrhea incidence [2,6,11,12].…”

“…In Morocco [8] and Honduras [9] serologic evi dence of Norwalk agent was found among travelers from the United States and there was no evidence of Rotavirus infection. In one survey carried out in Mexico, 25% of students with diarrhea and 12 % of well con trols had microscopic evidence of Rotavirus in their stools [29], Norwalk agent can be a problem for some groups traveling to Mexico [30].…”

Prevention and self-treatment of travelers' diarrhea

“…Some serologic evidence implicating norovirus as an agent of traveler's diarrhea has been reported: studies of Peace Corps volunteers in both Thailand (44) and Honduras (142) have demonstrated seroconversion following diarrheal episodes. Norovirus has particularly been implicated in outbreaks of traveler's diarrhea in certain situations, especially on cruise ships (16).…”

“…Early studies using either doxycycline (138,142) or trimethoprim-sulfamethoxazole (TMP-SMX) (37) showed that they were effective in preventing traveler's diarrhea in many parts of the world; however, widespread resistance to both of these agents has subsequently developed (79), thus limiting their usefulness.…”