Vesicular stomatitis virus (New Jersey strain) infection in two California dairy herds: an epidemiologic study

The course of vesicular stomatitis in cattle was investigated in 2 dairy herds (A and B) located in the southern San Joaquin Valley of California. Cattle were examined and specimens were obtained for virus isolation and for serologic survey for one year after an epizootic in December 1982. All 33 lactating cows selected for study had oral lesions, but only 19 (58%) were drooling or frothing around the mouth. Lesions on feet and teats were not observed. The healing time (longer than has been reported previously) for oral lesions ranged from 34 to 59 days. The mean serum neutralizing antibody titer for all cows tested in both herds 21 days after clinical signs were first observed was greater than 1:512. The mean titer decreased in the first 11 months after the epizootic, but remained greater than 1:128, and then increased during December 1983. Vesicular stomatitis virus/New Jersey strain was not isolated from 239 blood samples, 235 swab specimens of oral cavities, 38 swab specimens of oral epithelium, 206 urine specimens, or 232 fecal specimens collected from cows; however, it was isolated from tongue epithelium of 3 cows at 1, 4, and 21 days after signs of frothing were first noticed. For 20 lactating cows brought into dairy A during the epizootic, a mean time of 8.9 days elapsed between time of entry and appearance of clinical signs of vesicular stomatitis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Experimental transmission of rabbit syphilis

Rabbit syphilis was experimentally transmitted from clinical cases to healthy rabbits. The purpose was to evaluate changes in RPR titers during the course of infection and to detect the pathogenic organism. Two of three littermate rabbits were inoculated topically. One rabbit became symptomatic, with typical clinical signs on its genitalia about 8 weeks after inoculation and a marked rise in RPR titers, another remained asymptomatic with a moderate rise in titers, and the control rabbit remained negative. These results supported the specific relationship between clinical signs and RPR titers. Histopathological examination of the skin lesion from the symptomatic rabbit revealed spirochetes.     

Ability of CD8+ T cell anti-feline immunodeficiency virus (FIV) activity and FIV proviral DNA load in mononuclear cells in FIV-infected cats

We investigated the relationship between CD8+ T cell anti-feline immunodeficiency virus (FIV) activity and FIV proviral DNA load integrated in mononuclear cells. The anti-FIV activity and the proviral DNA load were correlated, and the number of proviral DNA copies was high in cats with decreased anti-FIV activity. Particularly, no anti-FIV activity was detected in the cats staged as having an acquired immunodeficiency syndrome (AIDS)-related complex or AIDS, and the number of proviral DNA copies was obviously increased compared to those in the cats in the asymptomatic stage. These results suggest that decreased anti-FIV activity destroys the control of in vivo FIV replication, which leads to an increased proviral DNA load with the progression of the clinical stage of disease.     

Macrolides and lincomycin susceptibility of Mycoplasma hyorhinis and variable mutation of domain II and V in 23S ribosomal RNA

A total of 151 strains of Mycoplasma hyorhinis isolated from porcine lung lesions (weaned pigs, n=71, and finishers, n=80) were investigated for their in vitro susceptibility to 10 antimicrobial agents. Thirty-one strains (28 from weaned pigs and 3 from finishers) showed resistance to 16-membered macrolide antibiotics and lincomycin. The prevalence of the 16-membered macrolide-resistant M. hyorhinis strain in weaned pigs from Japanese herds has approximately quadrupled in the past 10 years. Several of the 31 strains were examined for mutations in the 23S ribosomal RNA (rRNA). All field strains tested showed a transition of A to G at position 2059 of 23S rRNA-rendered Escherichia coli. On the other hand, individual tylosin- and lincomycin-resistant mutants of M. hyorhinis were selected in vitro from the susceptible type strain BTS7 by 3 to 9 serial passages in subinhibitory concentrations of each antibiotic. The 23S rRNA sequences of both tylosin and lincomycin-resistant mutants were compared with that of the radical BTS7 strain. The BTS7 mutant strain selected by tylosin showed the same transition as the field-isolated strains of A2059G. However, the transition selected in lincomycin showed mutations in domains II and V of 23S rRNA, G2597U, C2611U in domain V, and the addition of an adenine at the pentameric adenine loop in domain II. The strain selected by lincomycin showed an additional point mutation of A2062G selected by tylosin.     

Isolation of a human erythrocyte-adapted substrain of Babesia rodhaini and analysis of the merozoite surface protein gene sequences

Babesia rodhaini is a rodent hemoparasite closely related to B. microti, the major causative agent of human babesiosis. We tested the infectivity of B. rodhaini for human erythrocytes by using the SCID mouse model in which the circulating erythrocytes were replaced with those of humans. Initially, parasites grew very poorly in the mouse model, but a variant capable of propagating in human erythrocytes emerged after an adaptation period of three weeks. In an attempt to identify parasite proteins involved in the alteration of host cell preference, an expression cDNA library of B. rodhaini was constructed and screened with immune mouse sera. Although we were able to obtain three merozoite surface protein (MSP) genes, sequences of these genes from both the parental strain and human erythrocyte-adapted substrain were identical. Our results suggest that B. rodhaini has potential ability to infect human erythrocytes, but development of this ability may not be brought about by an amino acid change in MSPs.     

Melanocytic matricoma in a dog

We report a tumor that developed at the root of the tail in a male, 2-year-old Shih Tzu dog. Histologically, the tumor consisted of basaloid epithelial cells, with shadow cells and neoplastic melanocyte proliferation. Immunohistochemically, epithelial components were positive for keratin/cytokeratin but basaloid cells were negative. Mononuclear or multinuclear melanocytes were positive for vimentin, S-100 protein, and HMB-45. In conclusion, this dog was diagnosed with canine melanocytic matricoma on the basis of the similarity of the histologic and immunohistochemical features in humans, and it may be the first case in an animal.