Knowledge-based patient screening for rare and emerging infectious/parasitic diseases: a case study of brucellosis and murine typhus.

Many infectious and parasitic diseases, especially those newly emerging or reemerging, present a difficult diagnostic challenge because of their obscurity and low incidence. Important clues that could lead to an initial diagnosis are often overlooked, misinterpreted, not linked to a disease, or disregarded. We constructed a computer-based decision support system containing 223 infectious and parasitic diseases and used it to conduct a historical intervention study based on field investigation records of 200 cases of human brucellosis and 96 cases of murine typhus that occurred in Texas from 1980 through 1989. Knowledge-based screening showed that the average number of days from the initial patient visit to the time of correct diagnosis was significantly reduced (brucellosis-from 17.9 to 4.5 days, p = 0.0001, murine typhus-from 11.5 to 8.6 days, p = 0.001). This study demonstrates the potential value of knowledge-based patient screening for rare infectious and parasitic diseases.

Indirect hemagglutination for the diagnosis of Heterobilharzia americana infections in dogs.

An indirect hemagglutination test was developed for the diagnosis of canine schistosomiasis. Specific-pathogen-free dogs and dogs infected with a variety of other helminths were experimentally infected with Heterobilharzia americana. Sera collected at various times after the dogs were exposed to cercariae were evaluated. Glutaraldehyde-fixed sheep erythrocytes sensitized with whole adult worm antigens provided a stable antigen substrate when tested over a period of months. The test produced sensitive and specific diagnosis at an appropriate serum dilution. Serum dilutions less than 1:80 from dogs with other helminth infections resulted in nonspecific agglutination. By postexposure day 60, coinciding with the end of the prepatent period, serum titers of dogs infected only with H americana equaled, and then surpassed, those of the other dogs.

A new tick cell line derived from Boophilus microplus.

The Boophilus microplus IX tick cell line was developed from a primary embryonic cell culture derived from eggs six to nine days old. The cell line has been in culture since March 1979 and is currently maintained at 32 degrees C in medium consisting of equal parts of minimum essential medium an Leibovitz 15 medium supplemented with 20 per cent fetal bovine serum, 10 per cent tryptose phosphate broth and 0.1 per cent plasma albumin. A split ratio of 1:2 has been used for all subcultures and the cell line is now in its 26th passage. The cells are predominantly epithelial-like and of the male diploid chromosome number 21.

Miracidia hatching technique for diagnosis of canine schistosomiasis.

A method of processing feces with subsequent hatching of Heterobilharzia americana eggs was found to be preferable to saline sedimentation for the diagnosis of canine schistosomiasis. The feces were filtered and washed in 3 changes of 0.85% NaCl solution. The remaining sediment was flooded with distilled water to promote the hatching of viable eggs. Miracidia were subsequently observed, which confirmed infection in naturally infected raccoons and experimentally infected dogs.

A controlled evaluation of albendazole against natural infections with Fasciola hepatica and Fascioloides magna in cattle.

Albendazole administered to cattle at doses of 45, 35, 25, and 15 mg/kg of body weight reduced the number of viable Fasciola hepatica adults by 99.8%, 97.6%, 97.6%, and 95.7%, F hepatica immatures by 100%, 98.6%, 98.6% and 91.9% and Fascioloides magna by 96.5%, 99.1%, 94.0%, and 94.0%, respectively. Statistical evaluation by one-way analysis of variance, showed significant (P less than 0.05) differences in burdens of each fluke species between treated and untreated cattle, but differences in efficacy between any two of the four drug doses were not significant. Signs of toxicosis were not observed between the time of drug administration and slaughter 7 to 10 days later.

Evaluation of less than recommended dosages of levamisole phosphate for the treatment of gastrointestinal nematodes of cattle.

The anthelmintic activity of 3 dosages of injectable levamisole phosphate was evaluated in 84- to 145-kg calves from a herd of cattle with a history of heavy gastrointestinal nematode infections. Trichostrongylid egg counts in the calves varied from 450 to 700/g of feces. The anthelmintic was administered subcutaneously to 3 groups of 10 calves each, at the rate of 8 mg/kg of body weight (current manufacturer's recommendation), 6 mg/kg, and 4 mg/kg. A 4th group of 10 calves was utilized as untreated control calves. At necropsy, comparison of worm burdens between treated and untreated calves indicated apparent reductions (at 8 mg/kg, 6 mg/kg, and 4 mg/kg, respectively) for the various nematodes to be: Haemonchus placei adults-99.9, 100, and 98.3%; H placei L4-91.0, 94.0, 98.0%; O ostertagia late L4-93.8, 86.7, and 96.3%; Trichostrongylus axei adults-99.1, 100, and 100%; Cooperia spp adults-99.8, 99.5, and 99.5%; and Oesophagostomum radiatum adults-100, 100, and 100%. Statistical evaluation, by one-way analysis of variance, of the mean number of each species recovered showed significant (P less than 0.05) differences in the worm burdens between treated and untreated calves, but differences in efficacy between any 2 of the 3 drug dosages were not significant.

Treatment of Hymenolepis nana in hamsters with Yomesan (niclosamide)

Ground feed containing 0.33% active niclosamide fed ad libitum to hamsters for a period of 7 da eliminated Hymenolepis nana from all animals tested. Six- to 8-wk-old hamsters fed at 3 and 10 times the therapeutic dose were not adversely affected.