Section 8: Bites and Infestations

Insect “bites” Many effects of metazoal parasitism are attributed to bites. Some metazoa (insects in a loose sense) do indeed bite, and others sting, but what we frequently designate as insect bite is attachment for feeding. The result of such attachment looks like a bite and is sooner or later attended by pain, itching, or stinging. True bites and stings, however, are instantly painful; many have immediate or late, more baleful effects; and most are generally inflicted in self-defense or seemingly wanton offense, not for feeding.

Attachment for feeding is parasitism that may be silent for a while and then variably symptomatic. In a given region, common indigenous metazoa that cause cutaneous effects by a bite, sting, or attachment for feeding may be recognized or guessed from signs and symptoms. These two illustrations are representative. Figure 8-1 may be guessed with reasonable correctness to be mosquito “bites,” and Fig. 8-2, clustered on the lower leg and ankle, to be flea bites. Because different family members may have different degrees of sensitivity, it is possible that only one or several in the household will develop these lesions, and others will be spared.

Insect “bites” The location of bites gives important clues to the causative insects. Those pictured in Figs. 8-3 and 8-4 are unlikely to be from mosquitoes (which tend to bite on exposed areas of skin) or fleas (which tend to bite the ankles and lower legs). A variety of crawling insects and mites can cause lesions of this sort, including chiggers.

Chigger bites are caused by trombiculid mites. These mites live in tall grasses and weeds and are most active in summer and fall. They attach to the skin as one walks by and brushes up against the vegetation. Lesions tend to occur in areas that are warmer, moister, or covered by tight clothing. The intense itching may last for several days.

Insect “bites” Certain insects creep under clothes and bite when they reach a point of restriction such as a sock or belt. Figure 8-5 shows bite marks and vast edema on the penis. The assaulting insect may have been an ordinary one that merely took advantage of a child left undressed and unguarded.

When a subject has been bitten, stung, or fed upon, the consequent lesion may be typical at the time and in its course to resolution or may be modified by scratching, secondary infection, or idiosyncratic host response. In the case of the mosquito, the lesions may be ...