A 10-year-old 4.3-kg spayed female domestic shorthair cat presented to the primary veterinarian for a 1-month history of intermittent dyschezia.Physical examination findings at that time were unremarkable, except for palpation of a moderate amount of hard fecal material in an otherwise soft, apparently nonpainful abdomen.The primary veterinarian (not available) performed 3-view abdominal radiography, which reportedly showed constipation.An enema was performed, removing 5 to 6 inches of firm stool.The patient was conservatively managed with stool softeners and appetite stimulants.Four days later, the cat was referred to the University of Florida Small Animal Hospital for evaluation of continued dyschezia and inappetence.A CBC was clinically unremarkable.A serum biochemistry panel showed mild hyperglycemia (212 mg/dL; reference range, 72.1 to 156.1 mg/dL), slight hypermagnesemia (2.9 mg/dL; reference range, 1.9 to 2.6 mg/ dL), and moderately elevated creatine kinase (893 IU/L; reference range, 20 to 440 IU/L).Three-view abdominal radiographs were obtained (Figure 1).Formulate differential diagnoses, then continue reading. Diagnostic Imaging Findings and InterpretationAbdominal radiography revealed a smoothly marginated, locally extensive descending colonic wall thickening, extending from the level of L6-L7 into the pelvic canal to the level of the coxofemoral joints.Orad to the descending colonic thick-
Skin and subcutaneous tissues are the origin of most common neoplasms affecting dogs, accounting for approximately one third of all tumors encountered in the species. Surgical excision is frequently the best chance for a cure; determining factors influencing the success of excision are vital for surgical management of cases. This work examined the shrinkage of skin of various lengths from three sites in formalin for both dogs and cats. Tissues were measured on the animal (initial measurement), at the time of excision (post-removal), and after formalin fixation (post-fixation). While shrinkage after tissue removal was found in samples from the thorax, abdomen, and rear leg in dogs and from the rear leg in cats, no significant shrinkage due to formalin fixation was detected in any sample except for the thoracic samples from the dog. Therefore, when determining where to make incisions to effect a surgical cure, initial measurements should take into account tissue shrinkage effects.
The rickettsia Anaplasma marginale is the most prevalent tick-borne livestock pathogen worldwide and is a severe constraint to animal health. A. marginale establishes lifelong persistence in infected ruminants and these animals serve as a reservoir for ticks to acquire and transmit the pathogen. Within the mammalian host, A. marginale generates antigenic variants by changing a surface coat composed of numerous proteins. By sequencing and annotating the complete 1,197,687-bp genome of the St. Maries strain of A. marginale , we show that this surface coat is dominated by two families containing immunodominant proteins: the msp 2 superfamily and the msp 1 superfamily. Of the 949 annotated coding sequences, just 62 are predicted to be outer membrane proteins, and of these, 49 belong to one of these two superfamilies. The genome contains unusual functional pseudogenes that belong to the msp 2 superfamily and play an integral role in surface coat antigenic variation, and are thus distinctly different from pseudogenes described as byproducts of reductive evolution in other Rickettsiales .
Abstract Rhipicephalus sanguineus (Latreille) (Ixodida: Ixodidae) is a three‐host dog tick found worldwide that is able to complete its' entire lifecycle indoors. Options for the management of R. sanguineus are limited and its' control relies largely on only a few acaricidal active ingredients. Previous studies have confirmed permethrin resistance and fipronil tolerance in R. sanguineus populations, commonly conferred by metabolic detoxification or target site mutations. Herein, five strains of permethrin‐resistant and three strains of fipronil‐tolerant ticks were evaluated for metabolic resistance using synergists to block metabolic enzymes. Synergist studies were completed with triphenyl phosphate ( TPP ) for esterase inhibition, piperonyl butoxide ( PBO ) for cytochrome P450 inhibition, and diethyl maleate ( DEM ) for glutathione‐ S ‐transferase inhibition. Additionally, increased esterase activity was confirmed using gel electrophoresis. The most important metabolic detoxification mechanism in permethrin‐resistant ticks was increased esterase activity, followed by increased cytochrome P450 activity. The inhibition of metabolic enzymes did not have a marked impact on fipronil‐tolerant tick strains.
A new pathogen strain can penetrate an immune host population only if it can escape immunity generated against the original strain. This model is best understood with influenza viruses, in which genetic drift creates antigenically distinct strains that can spread through host populations despite the presence of immunity against previous strains. Whether this selection model for new strains applies to complex pathogens responsible for endemic persistent infections, such as anaplasmosis, relapsing fever, and sleeping sickness, remains untested. These complex pathogens undergo rapid within-host antigenic variation by using sets of chromosomally encoded variants. Consequently, immunity is developed against a large repertoire of variants, dramatically changing the scope of genetic change needed for a new strain to evade existing immunity and establish coexisting infection, termed strain superinfection. Here, we show that the diversity in the alleles encoding antigenic variants between strains of a highly antigenically variant pathogen was equal to the diversity within strains, reflecting equivalent selection for variants to overcome immunity at the host population level as within an individual host. This diversity among strains resulted in expression of nonoverlapping variants that allowed a new strain to evade immunity and establish superinfection. Furthermore, we demonstrated that a single distinct allele allows strain superinfection. These results indicate that there is strong selective pressure to increase the diversity of the variant repertoire beyond what is needed for persistence within an individual host and provide an explanation, competition at the host population level, for the large genomic commitment to variant gene families in persistent pathogens.
The remarkable genetic diversity of vector-borne pathogens allows for the establishment of superinfection in the mammalian host. To have a long-term impact on population strain structure, the introduced strains must also be transmitted by a vector population that has been exposed to the existing primary strain. The sequential exposure of the vector to multiple strains frequently prevents establishment of the second strain, a phenomenon termed superinfection exclusion. As a consequence, superinfection exclusion may greatly limit genetic diversity in the host population, which is difficult to reconcile with the high degree of genetic diversity maintained among vector-borne pathogens. Using Anaplasma marginale, a tick-borne bacterial pathogen of ruminants, we hypothesized that superinfection exclusion is temporally dependent and that longer intervals between strain exposures allow successful acquisition and transmission of a superinfecting strain. To test this hypothesis, we sequentially exposed Dermacentor andersoni ticks to two readily tick-transmissible strains of A. marginale The tick feedings were either immediately sequential or 28 days apart. Ticks were allowed to transmission feed and were individually assessed to determine if they were infected with one or both strains. The second strain was excluded from the tick when the exposure interval was brief but not when it was prolonged. Midguts and salivary glands of individual ticks were superinfected and transmission of both strains occurred only when the exposure interval was prolonged. These findings indicate that superinfection exclusion is temporally dependent, which helps to account for the differences in pathogen strain structure in tropical compared to temperate regions.Many vector-borne pathogens have marked genetic diversity, which influences pathogen traits such as transmissibility and virulence. The most successful strains are those that are preferentially transmitted by the vector. However, the factors that determine successful transmission of a particular strain are unknown. In the case of intracellular, bacterial, tick-borne pathogens, one potential factor is superinfection exclusion, in which colonization of ticks by the first strain of a pathogen it encounters prevents the transmission of a second strain. Using A. marginale, the most prevalent tick-borne pathogen of cattle worldwide, and its natural tick vector, we determined that superinfection exclusion occurs when the time between exposures to two strains is brief but not when it is prolonged. These findings suggest that superinfection exclusion may influence strain transmission in temperate regions, where tick activity is limited by season, but not in tropical regions, where ticks are active for long periods.
Magnetic resonance imaging is increasingly available for evaluation of horses with suspected pituitary adenomas; however, published studies describing the MRI features of normal equine pituitary glands are currently lacking. This retrospective, descriptive, anatomic study describes the MRI appearance and size of presumed normal equine pituitary glands and assesses potential correlations between pituitary size, brain size, and patient weight. These findings serve as a reference for MRI evaluation of the equine pituitary gland. Inclusion criteria consisted of adult horses (2-15 years old), over 300 kg with no evidence of Pituitary pars intermedia dysfunction (PPID) and no pituitary abnormalities identified with MRI, yielding 27 horses. Histology was available on seven pituitary glands; all were considered normal by a board-certified anatomic pathologist. Imaging features of the glands were evaluated on T2-weighted and pre- and postcontrast T1-weighted images. Pituitary length, width, and height and brain height and width were measured by two authors on transverse and mid-sagittal plane postcontrast T1 weighted images. The mean ± SD pituitary gland width was 21.0 ± 2.4 mm, height: 10.4 ± 1.9 mm, and length: 24.5 ± 2.7 mm. There were no significant correlations using a Pearson's correlation coefficient between pituitary and brain measurements, pituitary measurement, and body weight, or between brain measurements and body weight. A statistical difference was not identified using an unpaired t-test (p > 0.05) in pituitary and brain measurements between necropsied and non-necropsied horses. Relative to the cerebral white matter, all pituitary glands were isointense to slightly hyperintense on T1-weighted images and isointense on T2-weighted images, with the exception of a focal T1-weighted hyperintensity that was present in the caudal aspect of the pituitary gland in 88% of horses. All pituitary glands were homogenously contrast enhancing. Pituitary dimensions did not correlate with either brain size or body weight in horses.
