Fifteen mycoplasma-free chickens were contact exposed to five chickens that had been experimentally infected with one of three different strains (two field strains and one laboratory strain) of Mycoplasma synoviae (MS). Culture and polymerase chain reaction (PCR) were positive by 3 days postinoculation (PI) in the experimentally infected birds. Lateral transmission was found by 7-14 days postexposure. Positive serum plate agglutination (SPA) results were detected 3-4 wk after positive culture and/or PCR in individual birds. By 42 days PI, all the birds in the groups exposed to field strain K1858 or K3344 had become infected as determined by culture and PCR, whereas only half of the birds in the group exposed to laboratory strain WUV1853 had become infected. Because of the unanticipated lack of seroconversion to hemagglutination inhibition (HI) and enzyme-linked immunosorbent assay (ELISA) in infected chickens, the study was extended. Each group was split into two groups of 10 birds each, one of which was vaccinated with a live B1/LaSota Newcastle disease (ND) vaccine virus to determine if a viral respiratory challenge might incite a stronger antibody response to the mycoplasma infection. All the birds were tested for seroconversion 14 and 21 days later. Of the birds vaccinated for ND, a slightly greater number were MS positive by SPA than the nonvaccinated birds. This effect was not present 21 days after vaccination, and there was no significant difference in the MS HI results from these groups, suggesting that the viral respiratory infection had little direct impact on seroconversion. The virulent field strain (K3344) elicited a stronger MS antibody response than the other strains. All results from the MS ELISA were negative in all groups through 9 wk. Positive results from PCR analysis correlated well with culture results, whereas serologic tests did not detect MS infection for several weeks. Monitoring programs solely dependent on seroconversion may be inadequate for diagnosis and control of mycoplasma infections.

In vitro susceptibility of avian Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) to enrofloxacin, sarafloxacin, tylosin, and oxytetracycline was determined by a serial broth dilution method. The minimum inhibitory concentration (MIC) was recognized by a conversion of the pH indicator phenol red in culture media to a yellow color. Each isolate or type strain of mycoplasma was tested in two replicates. The MICs of tylosin, enrofloxacin, sarafloxacin, and oxytetracycline against five isolates and two reference strains of MG (approximately 10(5) colony-forming units [CFU]/ml) were 0.05, 0.14, 0.37, and 1.30 microg/ml, respectively. The MICs of the four antimicrobial agents against six isolates and one reference strain of MS (approximate 10(5) CFU/ml) were 0.13, 1.82, 1.76, and 0.91 microg/ml, respectively. There were no differences (P > 0.05) between tylosin, enrofloxacin, and sarafloxacin against MG, but these three antibiotics were different (P < 0.05) from oxytetracycline. The MIC value of tylosin against MS was different (P < 0.05) from those of sarafloxacin and enrofloxacin, but it was not different (P > 0.05) from that of oxytetracycline.

Infection with the nematode Deletrocephalus dimidiatus was found in the distal small and proximal large intestines of a 30-month-old female rhea that had died after a prolonged illness. Numerous strongyle-like eggs were found on fecal flotation. Possible treatments include fenbendazole (60 ppm in water) and ivermectin (200 mg/kg). Preventive measures such as artificial incubation, segregation of chicks from adults, and placing chicks in uncontaminated environments may help slow or stop the transmission of the parasite.

Five- and six-day-old broilers from two flocks experiencing excessive mortality were submitted for necropsy. Rickets was diagnosed based on clinical signs of lameness and on gross and histopathologic lesions. Because of a confirmed feed mill error, these flocks had been fed a starter ration with a high calcium/phosphorus ratio (either 7.7:1 or 3.5:1). After debate concerning the profitability of salvaging the remaining birds in the affected flocks, the starter feed was replaced at 7 days of age. At processing, the affected flocks had weighted averages of body weight and feed conversion of 1.71 kg and 1.88, respectively; these averages compared favorably with the company averages of 1.72 kg and 1.87. The majority of the mortality in the affected flocks occurred during the first week. This case report demonstrates that it may be advantageous for a producer to salvage chicks that have been affected severely with rickets at less than 1 week of age.