Experimental and field studies of Escherichia coli O157:H7 in white-tailed deer.

Studies were conducted to evaluate fecal shedding of Escherichia coli O157:H7 in a small group of inoculated deer, determine the prevalence of the bacterium in free-ranging white-tailed deer, and elucidate relationships between E. coli O157:H7 in wild deer and domestic cattle at the same site. Six young, white-tailed deer were orally administered 10(8) CFU of E. coli O157:H7. Inoculated deer were shedding E. coli O157:H7 by 1 day postinoculation (DPI) and continued to shed decreasing numbers of the bacteria throughout the 26-day trial. Horizontal transmission to an uninoculated deer was demonstrated. Although E. coli O157:H7 bacteria were recovered from the gastrointestinal tracts of deer necropsied from 4 to 26 DPI, attaching and effacing lesions were not apparent in any deer. Results are similar to those of inoculation studies in calves and sheep. In field studies, E. coli O157 was not detected in 310 fresh deer fecal samples collected from the ground. It was detected in feces, but not in meat, from 3 of 469 free-ranging deer in 1997. In 1998, E. coli O157 was not detected in 140 deer at the single positive site found in 1997; however, it was recovered from 13 of 305 dairy and beef cattle at the same location. Isolates of E. coli O157:H7 from deer and cattle at this site differed with respect to pulsed-field gel electrophoresis patterns and genes encoding Shiga toxins. The low overall prevalence of E. coli O157:H7 and the identification of only one site with positive deer suggest that wild deer are not a major reservoir of E. coli O157:H7 in the southeastern United States. However, there may be individual locations where deer sporadically harbor the bacterium, and venison should be handled with the same precautions recommended for beef, pork, and poultry.

Natural Mycoplasma gallisepticum infection in a captive flock of house finches.

Naturally-occurring mycoplasmal conjunctivitis is described among 104 wild-caught, and initially seronegative, house finches (Carpodacus mexicanus) maintained in captivity for 12 wk during November 1995 through January 1996. Finches housed in three pens were monitored for clinical signs, and > or = 10 birds were euthanatized for necropsy and mycoplasma testing every 2 wk. Within 2 to 4 wk following initial detection of lesions, > 50% of the birds in each of three pens developed a debilitating disease characterized by mild to severe ocular swelling, conjunctivitis, and ocular and nasal discharge. Microscopic lesions in affected finches consisted of mild to severe lymphoplasmacytic inflammation with epithelial and lymphoid hyperplasia in conjunctivae, nasal turbinates, and trachea. Mycoplasma gallisepticum infection was confirmed by culture or polymerase chain reaction (PCR) in all birds with conjunctival lesions and in 43% of birds without lesions. An arbitrary primer PCR was used to confirm M. gallisepticum isolates as identical to a field strain previously associated with house finch conjunctivitis. Most birds (89%) with conjunctivitis developed a concurrent antibody response detectable by serum plate agglutination (SPA) within 2 wk of lesion development. Hemagglutination inhibition (HI) and enzyme-linked immunosorbent assay (ELISA) tests were less sensitive than the SPA test. The clinical severity of this disease and high proportion of affected birds suggests that M. gallisepticum may have a negative impact on free-flying house finch populations.

Spontaneous cryptosporidiosis in captive white-tailed deer (Odocoileus virginianus).

In August 1994, cryptosporidiosis was diagnosed in a diarrheic fawn from a captive white-tailed deer (Odocoileus virginianus) herd maintained for research purposes at The University of Georgia's Warnell School of Forest Resources in Athens, Georgia (USA). From June through August 1995, 11 captive female white-tailed deer were housed in individual barn stalls where they gave birth to 18 fawns. Feces collected at 2 or 3 day intervals from the 18 neonatal fawns for at least 21 days and from 11 adult females once from 1 to 30 days before fawns were born and on three to 12 occasions after their birth were examined for oocysts of Cryptosporidium spp. Feces from all animals appeared normal throughout the period of examination. Oocysts morphologically indistinguishable from those of Cryptosporidium parvum were detected intermittently in the feces of one adult female from 1 to 25 days after parturition and in the feces of her fawn from 11 to 22 days of age. Oocysts also were detected intermittently in feces from twin fawns from 9 to 20 days of age, but not from their mother. Oocysts from deer were infectious for neonatal mice as determined histologically, and for calves as determined by clinical signs and excretion of oocysts.

Monitoring of Culicoides spp. at a site enzootic for hemorrhagic disease in white-tailed deer in Georgia, USA.

Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) were monitored at a Georgia (USA) site where epizootic hemorrhagic disease (EHD) and bluetongue (BT) viruses are enzootic among white-tailed deer (Odocoileus virginianus). Collections were made using a captive white-tailed deer and light traps from June 1993 through November 1994. We collected 210,482 females from the captive deer during morning and evening periods. Predominant species were C. lahillei (73%), C. stellifer (16%), C. biguttatus (6%), C. niger (3%), C. spinosus (2%), and C. paraensis (0.2%). Other species were C. venustus, C. obsoletus/sanguisuga, C. haematopotus, C. guttipennis, and C. arboricola, which together represented < 0.1% of the specimens collected. No C. variipennis, a known vector of EHD and BT viruses, were collected from the deer. An estimated 953,299 females were collected in 695 light-trap nights. The most common species in light-trap collections were C. spinosus (45%), C. biguttatus (27%) and C. stellifer (24%). Culicoides variipennis was rare in the light-trap samples, representing < 0.01% of the total collections. There was serological evidence from hunter-killed deer that local deer were infected with EHD and BT viruses during the study, particularly during 1994. A primary suspect vector was C. lahillei, which attacked the bait deer in large numbers during the summer and early fall of both 1993 and 1994. Based on their seasonality, relative abundance, and host-seeking activity, C. stellifer and C. spinosus also were considered as possible vectors. However, virus isolation attempts on 113,716 Culicoides, including 62,530 C. lahillei and 32,769 C. stellifer, were negative.