No abstract

Hen pheasants (Phasianus colchicus) injected with graded single doses of TCDD (6.25, 25, or 100 micrograms/kg) exhibited delayed-onset body weight loss and mortality--classic signs of the wasting syndrome. The lowest single dose of TCDD to produce this effect was 25 micrograms/kg. When hen pheasants were treated weekly with far lower doses of TCDD (0.01-1.0 microgram/kg/wk) for 10 wk, signs of the wasting syndrome and mortality were also produced. The lowest cumulative TCDD dose required to produce the response, using a weekly dosing regimen, was 10 micrograms/kg. Furthermore, using this dosing regimen, egg production by hens treated with a cumulative TCDD dose of 10 micrograms/kg was reduced, as was hatchability of their eggs. We conclude that hen pheasants are responsive to the overt toxic effects of TCDD and that the lowest cumulative dose of TCDD that produces overt signs of toxicity, 10 micrograms/kg, also reduces egg production and egg hatchability.

Deoxyribonucleic acid (DNA)-DNA hybridization was used to determine the relationships of Mycobacterium paratuberculosis and Mycobacterium avium to 24 mycobacterial strains representing seven species. Our results indicate that M . paratuberculosis should be considered a member of the same genomic species as M. avium and the wood pigeon bacillus. Mycobacterium scrofulaceum, which has been considered a member of the M . avium-Mycobacterium intracellulare-M. scrofulaceum complex on the basis of phenotypic characteristics, shows little DNA similarity to M . avium, M. intracellulare, or M. paratuberculosis.Classification of the slow-growing mycobacteria on the basis of phenotypic characteristics has been a complicated and uncertain process. There is relatively little variability among strains thought to typify separate species, and there is significant variation in the phenotypic characteristics of isolates which appear to belong to the same species (26,(33)(34)(35). This is particularly true of Mycobacterium paratuberculosis. Phenotypic variation within the species precludes identification of a clear pattern of biochemical responses in an Adansonian system. The characteristics exhibited by fresh isolates may change with storage or repeated passage (9, 26). Mycobactin dependency, hydrolysis of Tween 80, and catalase activity at pH 5 after heating are the characteristics which have been used to distinguish M . paratuberculosis from Mycobacterium avium. When these criteria are used, the wood pigeon bacillus (22, 33) resembles M . paratuberculosis rather than M . avium, as do some other M . avium isolates cultured from swine lymph nodes and lesions in birds (8,22,26,33).Antibiotic susceptibility patterns have been used in attempts to distinguish M . paratuberculosis from M . avium. M . paratuberculosis is often susceptible to streptomycin and rifampin, as well as to neotetrazolium chloride, whereas M . avium is usually resistant to all three antibiotics. These responses are also variable (9,34).Mycobacterium scrofulaceum has often been included as a member of the M . avium-Mycobacterium intracellulare-M. scrofulaceum (MAIS) complex on the basis of phenotypic characteristics (35), although the relationship of M. scrofulaceum to M . paratuberculosis has not been examined by other investigators.There is a need for better methods of defining the relationship of M . paratuberculosis to other mycobacterial species. Although numerous investigations on mycobacterial deoxyribonucleic acid (DNA)-DNA hybridization have been reported (3)(4)(5)7, 10, 13,16,17) MATERIALS AND METHODSBacterial strains. The 24 mycobacterial strains used in this study are listed in Table 1. The cells were grown in Middlebrook 7H9 medium supplemented with Dubos oleic-albumin complex (100 ml/liter) and 0.05% Tween 80 and were cultivated by standard methods (9). The M . paratuberculosis cultures were further supplemented with 2 mg of mycobactin J (Allied Laboratories, Inc., Ames, Iowa) per liter. Cells were pelleted by centrifugation at 6,000 x g for 15 min...

A DNA probe, M13 mpHAW71, that detects Mycobacterium paratuberculosis in the fecal material of infected animals was developed for use in the diagnosis of Johne's disease. The probe detected as few as IO' M. paratuberculosis when hybridized under stringent conditions to total genomic DNA purified from bovine fecal material. When the probe was used diagnostically, it did not differentiate members of the Mycobacterium avium-M. intracellulare-M. paratuberculosis complex. Compared with culturing, the DNA probe identified 34.4% more mycobacterium-containing fecal samples, and testing took only 72 h to complete.