Dale L. Brooks

Experimental oral inoculations in birds to evaluate potential definitive hosts of Neospora caninum

Experimental oral inoculations to evaluate potential definitive hosts of Neospora caninum were conducted by feeding infected rodent tissues to 9 carnivorous birds of 4 species. Birds included 2 red-tailed hawks (Buteo jamaicensis), 2 turkey vultures (Cathartes aura), 2 barn owls (Tyto alba), and 3 American crows (Corvus brachyrhynchus). The rodents (mice or rats) had been inoculated with 100,000 culture-derived tachyzoites of N. caninum 1-6 mo before feeding to the birds. Fecal samples were collected from each bird daily for 1 mo after feeding rodents and examined for oocysts by fecal flotation. In addition, processed aliquots from all avian fecal samples were fed to BALB/c mice. Five weeks after feeding, mice were bled and sera were tested for antibodies against N. caninum. One to two months later, mice were killed and brain tissue was examined microscopically for protozoal cysts. While occasional oocysts were found in avian fecal samples, these were likely not N. caninum because they were not infective to BALB/c mice. It was concluded that the bird species tested are not likely to be definitive hosts of N. caninum.

PASTEURELLA MULTOCIDA IN RAPTORS : PREVALENCE AND CHARACTERIZATION

Several cases dealing with Pasteurella multocida infection have been documented in raptors. However, the isolates have not been fully characterized nor has the prevalence of P. multocida in raptors been determined. Three hundred ninety-eight raptors were cultured for P. multocida. Results indicated that P. multocida was not normally carried in the pharyngeal, choanal, or cloacal regions. However, P. multocida was isolated from raptors with avian cholera. Isolates from eight cases were characterized by biotype, somatic serotype, and antibiogram. Most (six of eight) of the P. multocida isolates belonged to somatic serotype 1. The remaining two P. multocida isolates belonged to somatic serotypes 3 and 3,4. The majority of the isolates belonged to the subspecies multocida. All isolates were susceptible to penicillin G, sulfisoxazole, tetracycline, and trimethoprim-sulfamethoxazole. Various restriction site heterogeneities of P. multocida chromosomal DNA were found among the raptor isolates. Results indicated that isolates of P. multocida somatic serotype 1 from diurnal raptors were genetically related.

Incidence and risk factors for bumblefoot (pododermatitis) in rehabilitated raptors

A retrospective cohort study was conducted on 821 raptors of 12 representative species, admitted to the California Raptor Center (CRC), during 1980-1990. The incidence rate for bumblefoot was 52 cases per 100 bird-years at risk. Eagles and hawks (buteos) were more likely to develop bumblefoot, and did so earlier during their captivity than other species. Also, raptors admitted with a limb fracture had the greatest risk (OR = 4.2) of developing bumblefoot than any other condition on entry. Median time from admission to development of bumblefoot was 52 days, and median duration of bumblefoot was 23 days.

Lesions Associated with Pasteurella multocida Infection in Raptors

Several case reports attest to the pathogenicity of Pasteurella multocida in raptors; however, the pathologic syndromes have not been fully described. We describe here the lesions encountered in 22 avian cholera cases in raptors. Besides septicemia-related lesions, a unique syndrome of esophageal abscesses was noted in 8 of the 11 (73%) Buteo hawks that succumbed to avian cholera. Esophageal abscesses were not noted in birds belonging to the order Strigiformes (owls) or family Falconidae (falcons and their relatives). Thus, the presence of white plaques in both the oropharynx and esophagus of Buteo hawks may indicate a possible P. multocida infection and should be considered in the differential diagnosis. This study also documents the first cases of avian cholera in a rough-legged hawk (Buteo lagopus) and a flammulated owl (Otus flammeolus).

The effect of gas supersaturation on the growth of juvenile channel catfish, Ictalurus punctatus

Abstract Juvenile channel catfish, Ictalurus punctatus , were exposed to ΔPs ranging from −3 to 117 mm Hg for 35 days. Gas bubble trauma was observed at 76 and 117 mm Hg, but not at 36 or −3 mm Hg. The mortality in the 76 and 117 mm Hg treatments was 1% and 54%, respectively. Gas supersaturation had no effect on the growth of surviving fish at any level.

Occurrence and Species of Lice on Free-living and Captive Raptors in California

Abstract This study determined the occurrence and identity of chewing lice (Mallophaga) on 35 clinically healthy raptors presented with traumatic injuries at the California Raptor Center during the summers of 1993 and 1994. Samples of lice were collected and preserved in 70% ethanol during physical examinations within 24 hours of admission. Eleven species of chewing lice were collected and identified from 7 species of raptors, including 2 long-term captive birds. All louse species except 1 were on their usual, previously documented raptor hosts. Four of the 10 species of free-living birds examined had no lice, but their sample sizes were small (1–3 birds each). At least 1 bird from each of the other 6 raptor species harbored some lice, but only 2 species, an American kestrel (Falco sparverius) and a barn owl (Tyto alba) were sampled in useful numbers. One of 8 kestrels yielded lice (1 species), and 4 of 14 barn owls were infested with lice (representing 2 species). Two captive birds, a spotted owl (Strix occidentalis) and a Swainsons hawk (Buteo swainsoni), were infested with lice (1 species each) after 463 days and 1198 days in captivity, respectively.

Pasteurella multocida in Psittacines: Prevalence, Pathology, and Characterization of Isolates

Although the pathogenicity of Pasteurella multocida for psittacines (parrots and their relatives) has been documented in several case reports, the associated pathologic syndromes have not been well defined nor have the isolates been characterized. In addition, the prevalence of P. multocida in psittacines has not been determined. Three hundred twenty-eight psittacines (253 clinically healthy and 75 clinically ill) were cultured for P. multocida. Pasteurella multocida was not isolated from the pharynx, choana, or cloaca of psittacines. However, in five dead psittacines submitted for necropsy, P. multocida was isolated. These isolates were characterized, and all belonged to either somatic serotype 3 or 4,7. Pasteurella multocida somatic serotype 3 was isolated from psittacines with septicemia, whereas P. multocida somatic serotype 4,7 was isolated from psittacines with cutaneous lesions. The majority (four out of five) of the P. multocida isolates belonged to the subspecies multocida, and all isolates were susceptible to penicillin G, sulfisoxazole, gentamicin, erythromycin, tetracycline, and trimethoprim-sulfamethoxazole but resistant to streptomycin. DNA fingerprints demonstrated that isolates belonging to the same somatic serotype were genetically related. The isolate from a cockatiel that had been caught by a cat belonged to somatic serotype 3 and was not genetically related to the other two isolates belonging to this somatic serotype.

Effects of gas-supersaturated water on Rana catesbeiana tadpoles

Abstract Rana catesbeiana tadpoles were exposed to gas supersaturated water which resulted in inflation of the gastrointestinal tract with gas. Affected tadpoles floated on the surface, either with their left sides elevated or on their backs. These clinical signs, similar to those of gas bubble disease, could be reversed by reducing the dissolved gas levels. Based on post-exposure observation for 30 days, a 4-day exposure to a ΔP of 160 to 170 mm Hg had no effect on survival. A 10-day exposure increased mortality and the levels of systemic Aeromonas hydrophila bacteria, the etiology of a serious amphibian disease, “Redleg”. Bacterial levels returned to control levels after a 6-day recovery period.