Table 6.

Considerations when deciding whether to provide presumptive antimicrobial therapy after accidental exposures to parasites, before documenting infectiona

Factors related to the accidental exposure
 What is the likelihood that the exposure will result in infection and disease (Table 2), keeping in mind that sometimes even seemingly inconsequential exposures do so?
Factors related to the infection
 Could infection, if it develops, be severe (e.g., be life threatening or cause substantial morbidity)? Are severe manifestations likely to develop quickly, or are the initial manifestations of illness likely to be relatively mild?
 Are sensitive techniques available for detecting infection? If not, what could be the consequences of not detecting the infection or of detecting it late (e.g., development of chronic infection or more morbidity)?
Factors related to the laboratorian
 Is the person likely to comply with monitoring for clinical and laboratory evidence of infection?
 Is the person immunocompromised, or does the person have characteristics (e.g., pregnancy or advanced age) or medical disorders (e.g., diabetes or heart disease) that could affect the course of infection, influence how well symptoms (e.g., fever) would be tolerated, or increase the risk for side effects from the therapy? Is the person allergic to or otherwise intolerant of the relevant drugs?
Factors related to the therapy
 The threshold for administering presumptive therapy is generally low if highly effective, minimally toxic, and easily administrable therapy is readily available. Decisions about whether to treat presumptively are more difficult if the therapy is of moderate or uncertain efficacy, could cause substantial toxicity, or is difficult to administer. Consider the following:
   How effective is the therapy likely to be for treating infection caused by the species and strain of interest?
   Is the therapy active during the early stages of infection (e.g., during the hepatic stage of infection with Plasmodium spp.)? Is there evidence to suggest that early treatment improves outcome? Could a presumptive course of therapy that is shorter than the typical therapeutic course suppress infection and potentially result in delayed onset of clinical manifestations or in chronic infection?
   How quickly does the therapy act? If treatment is not started until after infection is documented, could the person become very sick before the therapy becomes effective?
   How toxic is the therapy in general, and is the person at hand at increased risk for particular toxicities?
  Drug availability
   Is the drug readily available? If not, how quickly can it be obtained?
  Ease of administration
   How is the drug administered (e.g., orally, intramuscularly, intravenously)?
   What is the duration of a typical course of therapy? Could the course be shortened if therapy is begun presumptively, soon after the exposure?
  • a Decisions about instituting presumptive therapy should be individualized. Although the answers to many of the questions in this list may not be known with certainty, the questions should prompt consideration of the listed factors. Irrespective of whether presumptive therapy is given, laboratorians with accidental exposure to parasites should be monitored for clinical and laboratory evidence of infection.