Urocanic acid is produced by deamination of histidine ( 14) and is abundant in mammalian skin ( 15). stercoralis, and larvae were not attracted to an extract of feline origin. stercoralis felines, in contrast, are rarely infected by S. In these preliminary experiments, the larvae also responded positively to an aqueous extract of skin from gerbils, which are a permissive experimental host for S. Attractant activity was recovered in the filtrate after ultrafiltration through Amicon membranes (Millipore, Billerica, MA) with nominal molecular weight cut-offs from 30,000 to 500 Da. Preliminary experiments showed that attractant activity was retained after heating of the attractant for 10 min at 80☌ or digestion with trypsin (0.25% for 30 min). 2 shows a family of dose–response curves illustrating larval attraction to such an extract at a series of dilutions. Inspection of the tracks left by larvae as they migrate toward a well containing crude or purified attractant showed that, even from a distance of 30 mm, migration is strongly directed toward the sample well ( Fig. stercoralis, the infective larvae of this parasite are attracted to a crude aqueous extract of canine skin. Resultsīecause dogs, along with humans and other primates, are natural hosts of S. ![]() Here we report the isolation and identification of a chemoattractant that, when provided either as a natural product or as a reagent chemical, attracts infective larvae in an in vitro system. Neurons that detect thermal gradients and some chemical signals have been identified and are considered to be important in host-finding ( 9, 10) however, the specific chemical signals that attract skin-penetrating infective larvae to the host have yet to be determined. stercoralis, a parasitic nematode that is more easily maintained in the laboratory. These systems, however, are being described in S. The host-finding behavior of the free-living infective larvae of the two major hookworms of humans has only recently been analyzed and described in detail ( 8) the host-provided chemical signals involved in skin penetration have been identified, but those involved in host-finding remain unknown, as do the signal transduction systems resulting in parasite growth and development. Thus, fatalities occur even in sophisticated hospital facilities in highly developed countries ( 6, 7).Įven though soilborne, skin-penetrating nematode parasites cause ill health throughout much of the world and have the adverse socioeconomic effects described above, little is known about the sequence of biological and physicochemical events that constitute the infective process ( 1), the process one would wish to interrupt to prevent infection. In patients who are immunosuppressed, either as a result of intercurrent disease or intentionally, as a consequence of treatment, the parasite can multiply internally to fatal levels of abundance. It is sometimes an HIV-associated nematode. The threadworm Strongyloides stercoralis parasitizes 300 million people globally ( 5). Consequently, these parasites have a major socioeconomic and medical impact ( 2, 4). ![]() Hookworms are the causative agents of ill health, diminished work capacity, depressed physical and cognitive development in children, and poor school performance. The hookworms Ancylostoma duodenale and Nector americanus parasitize >600 million people globally and contribute significantly to widespread iron-deficiency anemia in the tropical and subtropical world. From both a medical and socioeconomic standpoint, skin-penetrating nematodes are among the most important helminth parasites of humans ( 1– 3).
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