Mark A. Mitchell

SOURCES AND RESERVOIRS OF TOXOPLASMA GONDII INFECTION ON 47 SWINE FARMS IN ILLINOIS

Field studies were conducted on 47 swine farms in Illinois during 1992 and 1993 to identify sources and reservoirs of Toxoplasma gondii infection. Blood samples were obtained from swine and from trapped wildlife. Serum antibodies to T. gondii were determined using the modified agglutination test, incorporating mercaptoethanol. Antibodies to T. gondii (titer > or = 25) were found in 97 of 4,252 (2.3%) finishing pigs, 395 of 2,617 (15.1%) sows, 267 of 391 (68.3%) cats, 126 of 188 (67.0%) raccoons, 7 of 18 (38.9%) skunks, 29 of 128 opossums (22.7%), 6 of 95 (6.3%) rats, 3 of 61 (4.9%) white-footed mice (Peromyscus sp.), and 26 of 1,243 (2.1%) house mice (Mus musculus). Brains and hearts of rodents trapped on the farm were bioassayed in mice for the presence of T. gondii. Toxoplasma gondii was recovered from tissues of 7 of 1,502 (0.5%) house mice, 2 of 67 (3.0%) white-footed mice, and 1 of 107 (0.9%) rats. Feces of 274 cats trapped on the farm and samples of feed, water, and soil were bioassayed in mice for the presence of T. gondii oocysts. Toxoplasma gondii was isolated from 2 of 491 (0.4%) feed samples, 1 of 79 (1.3%) soil samples, and 5 of 274 (1.8%) samples of cat feces. All mammalian species examined were reservoirs of T. gondii infection. All farms had evidence of T. gondii infection either by detection of antibodies in swine or other mammalian species, or by detection of oocysts, or by recovery from rodents by bioassay. The possibility of transmission of T. gondii to swine via consumption of rodents, feed, and soil was confirmed.

Risk factors for transmission of Toxoplasma gondii on swine farms in Illinois

Two epidemiologic studies of risk factors for transmission of Toxoplasma gondii to swine were conducted for farms in Illinois. The first study was a cross-sectional survey of swine farms from the state of Illinois pseudorabies testing program, in which farm owners or managers were interviewed by telephone regarding presence of risk factors for transmission of T. gondii on the farm. There were 123 farms surveyed that provided blood samples for at least 30 sows. The mean sow seroprevalence was 19.5% (median = 10.0%). Multiple regression analysis of the association of sow seroprevalence with outdoor housing of sows, cat access to sow areas, number of sows, open feed storage and water delivery, delayed removal of carcasses, and presence of rodents on the farm indicated that higher sow seroprevalence was associated with cat access to sows (P = 0.009) and fewer sows in the herd (P = 0.05). The second study was a field investigation of 47 swine farms (37 from the cross-sectional study). Data collection included obtaining blood samples from swine, cats, and rodents, and fecal samples from cats, heart and brain tissue from rodents, and feed, water, and soil samples for T. gondii examination. The risk of T. gondii transmission from cats and rodents to sows and finishing pigs was evaluated, taking into account housing conditions and herd size. Multiple regression analysis indicated that T. gondii seroprevalence in finishing pigs increased with more seropositive juvenile cats on the farm (P < 0.0001) and higher seroprevalence in house mice (P = 0.0023).(ABSTRACT TRUNCATED AT 250 WORDS)

SEROLOGIC SURVEY FOR SELECTED INFECTIOUS DISEASE AGENTS IN RACCOONS FROM ILLINOIS

The determination of serologic titers to infectious organisms is a valuable tool for quantitating exposure to disease organisms. Raccoons (Procyon lotor) were live-trapped from September 1989 to October 1993 and samples collected from two distinct locations in west-central Illinois (USA); a state recreational facility (Park) and privately owned farming property (Farm). Sera were submitted for testing Leptospira interrogans (serovars bratislava, canicola, grippotyphosa, hardjo, icterohemmorhagiae, and pomona), canine distemper virus (CDV), pseudorabies virus (PV), and Toxoplasma gondii. Two-hundred and twenty-two (48%) of 459 raccoons were seropositive for L. interrogans. Eighty-five (23%) out of 368 raccoons were seropositive for canine distemper virus. Eighty-two (17%) of 479 raccoons raccoons were seropositive for pseudorabies virus. One hundred and eighty-four (49%) of 379 raccoons were seropositive for T. gondii. A significant difference (P < 0.05) in seroprevalence for L. interrogans between the park (43%) and farm (52%) areas was found. A correlation between increasing age and seroprevalence was found for L. interrogans, CDV, PV, and T. gondii. Furthermore, there was a significant difference in seroprevalence for T. gondii during the spring trapping seasons (73%), when compared with the fall (33%). This type of information on exposure to infectious agents is important for developing control programs to manage raccoon-human and raccoon-domestic animals interactions.

Parastrongylus (=Angiostrongylus) cantonensis Now Endemic in Louisiana Wildlife

Parastrongylus (=Angiostrongylus) cantonensis, a lung worm of rats, was first reported in the United States in 1987, with a probable introduction by infected rats from ships docking in New Orleans, Louisiana, during the mid-1980s. Since then, it has been reported in nonhuman primates and a boy from New Orleans, and in a horse from Picayune, Mississippi, a distance of 87 km from New Orleans. Parastrongylus cantonensis infection is herein reported in a lemur (Varencia variegata rubra) from New Iberia, Louisiana, a distance of 222 km from New Orleans, and in a wood rat (Neotoma floridanus) and in 4 opossums (Didelphis virginiana) from Baton Rouge, Louisiana, a distance of 124 km from New Orleans. The potential of a great variety of gastropods serving as intermediate hosts in Louisiana may pose a threat to wildlife as well as to domesticated animals in the areas where infected Norway rats (Rattus norvegicus) are present.

Preliminary findings of Salmonella spp. in captive green iguanas (Iguana iguana) and their environment

Captive reptiles are routinely identified as reservoirs of Salmonella spp. and reports of reptile-associated salmonellosis are increasing. Unfortunately, little is known about the epidemiology of Salmonella spp. and green iguanas. We did a limited survey of a green-iguana farm in El Salvador to identify sources of Salmonella spp. in green iguanas and their environment. A limited number of samples for microbiological culture were collected from iguanas (adult, hatchling, and embryos) and their environment (food, water, soil, shelter, insects, and wild-caught lizards). Salmonella spp. was isolated from the intestine of both adult (3/20) and hatchling iguanas (8/20). There was no evidence of Salmonella spp. in the reproductive tracts of female iguanas (0/10). Salmonella spp. was isolated from the surface of 40% (7/16) of the egg surfaces tested. Salmonella spp. was not identified from the externalized yolk-sac of the iguana embryos tested. Soil samples from a breeding pen and a nest were both positive for Salmonella spp. Eight different Salmonella spp. serotypes were identified in this survey. These results suggest that horizontal transmission of Salmonella spp. is a potential source of exposure to hatchling iguanas at this facility.

High Costs of Female Choice in a Lekking Lizard

Although the cost of mate choice is an essential component of the evolution and maintenance of sexual selection, the energetic cost of female choice has not previously been assessed directly. Here we report that females can incur high energetic costs as a result of discriminating among potential mates. We used heart rate biologging to quantify energetic expenditure in lek-mating female Galápagos marine iguanas (Amblyrhynchus cristatus). Receptive females spent 78.9±23.2 kJ of energy on mate choice over a 30-day period, which is equivalent to ∼¾ of one days energy budget. Females that spent more time on the territories of high-quality, high-activity males displayed greater energetic expenditure on mate choice, lost more mass, and showed a trend towards producing smaller follicles. Choosy females also appear to face a reduced probability of survival if El Niño conditions occur in the year following breeding. These findings indicate that female choice can carry significant costs, and suggest that the benefits that lek-mating females gain through mating with a preferred male may be higher than previously predicted.

Evaluation of Medetomidine, Clove Oil and Propofol for Anesthesia of Leopard Frogs, Rana pipiens

ABSTRACT The clinical effects of medetomidine, clove oil and propofol were evaluated in 36 clinically healthy leopard frogs, Rana pipiens. Under controlled laboratory conditions, heart and respiratory rates were measured at defined intervals during each trial. Corneal, superficial and deep pain withdrawal and righting reflexes were evaluated over time following a single drug administration. Medetomidine (150 μ/kg) failed to produce clinically apparent sedation in any of the frogs (n=12) despite a reduction in respiratory rate. Immersion in a clove oil (eugenol) bath (310 - 318 mg/L for 15 min) induced surgical anesthesia in all frogs (n=12). However, the duration of anesthesia was variable, ranging from less than 5 min to 65 min. Gastric prolapse was a common side effect of clove oil anesthesia (50%, 6/12) but the significance of this effect is unclear. Propofol (10 mg/kg) injected perivascularly in the sublingual plexus area induced sedation in all frogs (n=12) and light anesthesia in 58% (7/12). Propofo...

Agreement between direct and indirect blood pressure measurements obtained from anesthetized Hispaniolan Amazon parrots

OBJECTIVE To determine the level of agreement between direct and indirect blood pressure measurements obtained from healthy Hispaniolan Amazon parrots (Amazona ventralis) anesthetized with isoflurane. DESIGN Validation study. ANIMALS 16 healthy adult Hispaniolan Amazon parrots. PROCEDURES Parrots were anesthetized, and a 26-gauge, 19-mm catheter was placed percutaneously in the superficial ulnar artery for direct measurement of systolic, mean, and diastolic arterial pressures. Indirect blood pressure measurements were obtained with a Doppler ultrasonic flow detector and an oscillometric unit. The Bland-Altman method was used to compare direct and indirect blood pressure values. RESULTS There was substantial disagreement between direct systolic arterial blood pressure and indirect blood pressure measurements obtained with the Doppler detector from the wing (bias, 24 mm Hg; limits of agreement, -37 to 85 mm Hg) and from the leg (bias, 14 mm Hg; limits of agreement, -14 to 42 mm Hg). Attempts to obtain indirect blood pressure measurements with the oscillometric unit were unsuccessful. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that there was substantial disagreement between indirect blood pressure measurements obtained with a Doppler ultrasonic flow detector in anesthetized Hispaniolan Amazon parrots and directly measured systolic arterial blood pressure.

Evaluation of Novaluron as a Feed-Through Insecticide for Control of Immature Sand Flies (Diptera: Psychodidae)

Abstract The development and survival of sand fly Phlebotomus papatasi Scopoli (Diptera: Psychodidae) larvae fed feces of Syrian hamsters, Mesocricetus auratus, that had been fed a diet containing novaluron were evaluated. In total, six larval diets were used in sand fly larval bioassays. Four groups of larvae were fed feces of hamsters that had been maintained on a diet containing either 0, 9.88, 98.8, or 988 ppm novaluron. Two additional groups were fed a larval diet composed of equal parts composted rabbit feces and rabbit chow containing either 0 or 988 ppm novaluron. No pupation, hence no adult emergence, occurred when larvae were fed feces of hamsters that were fed diets containing novaluron. The mortality of sand flies fed feces of treated hamsters occurred during larval molts. The results of this study suggest that a control strategy using rodent baits containing novaluron to control phlebotomine sand flies and zoonotic cutaneous leishmaniasis may be possible.

Diagnosis and management of reptile orthopedic injuries

As veterinarians expand their understanding of the specific husbandry requirements for captive reptiles, nutritionally associated orthopedic injuries should decrease. Orthopedic injuries in wild reptiles, however, will continue to increase as new infrastructure encroaches on the habitats of these animals. Research should be pursued that focuses on improving our understanding of pain management in reptiles, on developing techniques to expedite bone healing, and on creating new orthopedic techniques that provide rigid stabilization without the use of temperature-sensitive materials.