A replication analysis of foot-and-mouth disease virus in swine lymphoid tissue might indicate a putative carrier stage in pigs

ABSTRACT: Foot-and-mouth disease virus (FMVD), one of the most contagious viruses of cloven-hoofed animals, may cause a prolonged, asymptomatic but persistent infection in ruminants, named the "carrier state". However, it remains an open question whether this carrier state occurs in pigs. Here we present quantitative analyses of the duration of FMDV RNA and infectivity in lymphoid and epithelial tissues in experimentally infected pigs with FMDV C-S8c1. The data indicated that although FMDV RNA remained in blood until day 14 post-infection (pi), viremia was cleared by day 7 pi. However, all tissues tested were positive for FMDV until day 14-17 pi. Interestingly, the specific infectivity of FMDV in these tissues was in some cases even higher than the FMDV C-S8c1. We therefore propose that a "pseudopersistent state" may occur in pigs in which virus replicates in lymphoid tissues for a prolonged period of time, thereby representing a potential source of virus.     

Effect of diet and tylosin on chronic diarrhea in beagles

Seven beagles in a colony of dogs had chronic diarrhea for at least 30 days. The dogs were subsequently treated with tylosin 20 mg/kg BW q24h PO for 10 days. During the treatment period, the feces became firmer but remained loose. When the treatment was discontinued, the diarrhea reappeared in 3 weeks. The feces remained abnormally loose in all dogs treated with metronidazole, trimethoprim-sulfadiazine, or doxycycline and prednisone. The diet was then changed for 10 days from a highly digestible moist pet food to a dry food developed for normal adult dogs. The feces again became firmer, although still loose in some dogs. The period was then extended to 3 month, but the fecal consistency continued to fluctuate from ideal to diarrhea. The dogs were treated a 2nd time with tylosin 20 mg/kg BW q24h PO for 10 days. The feces then became significantly firmer and remained so throughout a 3-month follow-up. We conclude that the combination of diet and tylosin was more effective than either agent alone in control of chronic diarrhea.     

A true "triphasic" pattern: thoracolumbar spinal tumor in a young dog

An 8-month-old male Bernese Mountain Dog was referred with a history of hindlimb weakness that progressed to paresis on the right side. An intradural mass was detected in the spinal canal at the level of the 2nd and 3rd lumbar vertebrae. During surgical removal, 2 small fragments of the mass were prepared for cytologic examination by the squash technique. Cytologic examination revealed 3 different cell types: mesenchymal (stromal) cells, epithelial cells, and small undifferentiated hyperchromatic cells. On the basis of location and the triphasic cytologic pattern, a diagnosis of spinal nephroblastoma (thoracolumbar spinal tumor of young dogs) was made; histologic examination of the mass confirmed the cytologic diagnosis. To our knowledge, this is the first report of a triphasic pattern in a cytologic sample; recognizing this pattern is an important aid in reaching a definitive cytologic diagnosis.     

DNA barcoding for identification of cryptic species in the field and existing museum collections: a case study of Aethomys and Micaelamys (Rodentia: Muridae)

DNA barcoding has been proposed as a method for species identification. However, this method has been criticised for its over-reliance on a single mitochondrial gene. In this study, four mitochondrial gene regions and one nuclear gene region were used to investigate their different abilities to identify tissue associated with museum specimens of Aethomys chrysophilus, Aethomys ineptus and Micaelamys namaquensis. Aethomys chrysophilus and the more recently elevated A. ineptus are indistinguishable on morphological grounds; however, their ranges are largely parapatric with only one syntopic locality currently known. All of the mitochondrial gene regions were able to separate M. namaquensis from A. chrysophilus and A. ineptus, but they varied in their abilities to resolve differences between A. chrysophilus and A. ineptus. The sequence results identified a specimen from KwaZulu-Natal that was misclassified and should have been identified as A. ineptus. Seven specimens that had not been reclassified following the elevation of A. ineptus to species level were identified as A. ineptus. Individuals of A. chrysophilus from Malawi could not be classified as either A. chrysophilus or A. ineptus, and may be a hybrid or a new, distinct species. This study indicates that DNA barcoding may be used to separate M. namaquensis from A. chrysophilus and A. ineptus, and although it was not able to separate A. chrysophilus and A. ineptus, it did indicate specimens from Malawi may be a new cryptic species.     

Effect of tylosin on dogs with suspected tylosin-responsive diarrhea: a placebo-controlled,randomized, double-blinded,prospective clinical trial

Background

The macrolid antibiotic tylosin has been widely used to treat canine chronic diarrhea, although its efficacy is based on anecdotal reports and experimental studies in dogs and not on strong scientific evidence. The term tylosin-responsive diarrhea (TRD) refers to diarrheal disorders responding to tylosin therapy within a few days. In TRD, the stool remains normal as long as tylosin treatment continues, but diarrhea reappears in many dogs within weeks after discontinuation. The aim of our trial was to assess the effect of tylosin on fecal consistency compared with a placebo treatment in dogs with suspected TRD and additionally to establish whether tylosin in dogs with recurrent diarrhea is as effective as empirical studies and anecdotal reports suggest.

Methods

Subjects comprised 71 client-owned dogs that, according to the owners, had previously been treated successfully with tylosin due to recurrent diarrhea of unknown etiology. At the initial examination, where there were no signs of diarrhea, the dogs were randomly assigned in a 2:1 ratio to a tylosin or placebo group. During a two-month follow-up the owners evaluated the fecal consistency according to previously published guidelines. When diarrhea recurred, either tylosin (25 mg/kg q 24 h, 7 days) or placebo treatment was initiated orally. Treatment outcome was evaluated as the mean of fecal consistency scores assigned during the last three days of the treatment period. To test for differences between the tylosin and placebo group in the proportion of responders, Pearson''s Chi-squared test and Fisher''s exact test were applied.

Results

Sixty-one dogs met the selection criteria and were followed for two months. During the follow-up 27 dogs developed diarrhea and either tylosin or placebo treatment was started. The proportion of dogs with normal fecal consistency at the end of treatment was 85% (17/20) in the tylosin group and 29% (2/7) in the placebo group (Pearson''s Chi-squared test p = 0.0049 and Fisher''s exact test two-sided, p = 0.0114).

Conclusions

Our findings indicate that tylosin is effective in treating recurrent diarrhea in dogs. The dose of 25 mg/kg once daily appears sufficient. No changes specific to TRD were detected in the examinations.