Elizabeth W Howerth

Publications of Elizabeth W Howerth

• Conservative management of a transverse fracture of the distal phalanx in a Quarter Horse.

  Authors: Ceri E Sherlock, Randall B Eggleston, Elizabeth W Howerth

  Journal of the American Veterinary Medical Association. 01/2012; 240(1):82-6.

  A 7-year-old Quarter Horse gelding was evaluated because of sudden onset of severe left forelimb lameness of 4 days' duration. Clinical evaluation and diagnostic perineural analgesia localized theA 7-year-old Quarter Horse gelding was evaluated because of sudden onset of severe left forelimb lameness of 4 days' duration. Clinical evaluation and diagnostic perineural analgesia localized the lameness to the distal portion of the left forelimb. Radiography revealed a transverse fracture of the distal phalanx of the left forelimb. The horse was treated conservatively with stall rest and stabilization of the hoof with fiberglass cast material and an elevated heel support. These treatments improved the lameness considerably. Over the following 4 months, the horse was exercised at an increasing level; external coaptation of the hoof was removed, and the horse was gradually shod in a flat shoe. At 6 months after injury, the horse had no signs of lameness when working at its previous performance level, but it was euthanized for reasons unrelated to orthopedic disease. Radiographically, the fracture was unapparent; however, results of magnetic resonance imaging and histologic examination of the cadaveric limb confirmed the presence of tissue changes consistent with a healing fracture. Conservative management of transverse fractures of the distal phalanx of a forelimb may be effective and enable affected horses to be returned to their intended use.

• Pathology in practice. Mannheimia haemolytica.

  Authors: Sylvia H Ferguson, Raquel R Rech, Elizabeth W Howerth

  Journal of the American Veterinary Medical Association. 12/2011; 239(11):1437-9.

• Pathology in practice. Mycotic abortion.

  Authors: Alexandria D Glover, Raquel R Rech, Elizabeth W Howerth

  Journal of the American Veterinary Medical Association. 08/2011; 239(3):319-21.

• Clinicopathologic findings in a dog with a retrobulbar meningioma.

  Authors: Daniel P Regan, Marc Kent, Rachael Mathes, Frederic S Almy, Phillip A Moore, Elizabeth W Howerth

  Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc. 07/2011; 23(4):857-62.

  An 11-year-old Fox Terrier dog was evaluated for a 10-month history of progressive exophthalmia and visual deficits in the right eye. Ophthalmologic examination revealed severe corneal fibrosis andAn 11-year-old Fox Terrier dog was evaluated for a 10-month history of progressive exophthalmia and visual deficits in the right eye. Ophthalmologic examination revealed severe corneal fibrosis and pigmentation, which obscured examination of the anterior chamber of the right eye. There was decreased retropulsion of the right eye. Neurological examination revealed an absent menace response bilaterally. Pupillary light reflex was normal in the left eye. Due to the corneal pathology, pupillary light reflex was unable to be evaluated in the right eye. A retrobulbar mass with heterogeneous echotexture was identified using ultrasonography. Cytological evaluation of a fine-needle aspirate of the mass disclosed a neoplastic cell population consisting of round to polygonal cells with lightly basophilic to gray cytoplasm and round to ovoid nuclei having a coarse granular chromatin pattern. Magnetic resonance imaging disclosed a right-sided retrobulbar mass that extended through the optic canal and was contiguous with an extra-axial mass in the ventral right rostral and middle cranial fossae. The mass displayed homogenous and strong contrast enhancement. Following exenteration, histological examination of the retrobulbar mass was consistent with meningioma. Immunohistochemically, tumor cells stained positive for vimentin (cytoplasmic) and E-cadherin (membranous), and negative for S100, pancytokeratin, and cytokeratins AE1 and AE3.

• Multisystemic infection with an Acanthamoeba sp in a dog.

  Authors: Marc Kent, Simon R Platt, Raquel R Rech, Joseph S Eagleson, Elizabeth W Howerth, Megan Shoff, Paul A Fuerst, Greg Booton, Govinda S Visvesvara, Scott J Schatzberg

  Journal of the American Veterinary Medical Association. 06/2011; 238(11):1476-81.

  CASE DESCRIPTION-A 10-month-old Boxer was evaluated for fever and signs of cervical pain. CLINICAL FINDINGS-Physical examination revealed lethargy, fever, and mucopurulent ocular and preputialCASE DESCRIPTION-A 10-month-old Boxer was evaluated for fever and signs of cervical pain. CLINICAL FINDINGS-Physical examination revealed lethargy, fever, and mucopurulent ocular and preputial discharge. On neurologic examination, the gait was characterized by a short stride. The dog kept its head flexed and resisted movement of the neck, consistent with cervical pain. Clinicopathologic findings included neutrophilic leukocytosis, a left shift, and monocytosis. Cervical radiographs were unremarkable. Cerebrospinal fluid analysis revealed neutrophilic pleocytosis and high total protein content. On the basis of signalment, history, and clinicopathologic data, a diagnosis of steroid-responsive meningitis-arteritis was made. TREATMENT AND OUTCOME: The dog was treated with prednisone (3.2 mg/kg [1.45 mg/lb], PO, q 24 h), for 3 weeks with limited response. Consequently, azathioprine (2 mg/kg [0.9 mg/lb], PO, q 24 h) was administered. Three weeks later, the dog was evaluated for tachypnea and lethargy. Complete blood count revealed leukopenia, neutropenia, and a left shift. Thoracic radiography revealed a diffuse bronchointerstitial pattern. The dog subsequently went into respiratory arrest and died. On histologic evaluation, amoebic organisms were observed in the lungs, kidneys, and meninges of the brain and spinal cord. A unique Acanthamoeba sp was identified by use of PCR assay. CLINICAL RELEVANCE: This dog developed systemic amoebic infection presumed to be secondary to immunosuppression. The development of secondary infection should be considered in animals undergoing immunosuppression for immune-mediated disease that develop clinical signs unrelated to the primary disease. Although uncommon, amoebic infection may develop in immunosuppressed animals. Use of a PCR assay for identification of Acanthamoeba spp may provide an antemortem diagnosis.

• Variation in viral shedding patterns between different wild bird species infected experimentally with low-pathogenicity avian influenza viruses that originated from wild birds.

  Authors: Taiana P Costa, Justin D Brown, Elizabeth W Howerth, David E Stallknecht

  Avian pathology : journal of the W.V.P.A. 04/2011; 40(2):119-24.

  The prevalence of infection with avian influenza (AI) virus varies significantly between taxonomic Orders and even between species within the same Order. The current understanding of AI infection andThe prevalence of infection with avian influenza (AI) virus varies significantly between taxonomic Orders and even between species within the same Order. The current understanding of AI infection and virus shedding parameters in wild birds is limited and largely based on trials conducted in mallards (Anas platyrhynchos). The objective of the present study was to provide experimental data to examine species-related differences in susceptibility and viral shedding associated with wild bird-origin low-pathogenicity avian influenza (LPAI) viruses in multiple duck species and gulls. Thus mallards, redheads (Aythya americana), wood ducks (Aix sponsa), and laughing gulls (Leucophaeus atricilla) were inoculated experimentally with three wild mallard-origin LPAI viruses representing multiple subtypes. Variation in susceptibility and patterns of viral shedding associated with LPAI virus infection was evident between the duck and gull species. Consistent with the literature, mallards excreted virus predominantly via the gastrointestinal tract. In wood ducks, redheads, and laughing gulls, AI virus was detected more often in oropharyngeal swabs than cloacal swabs. The results of this study suggest that LPAI shedding varies between taxonomically related avian species. Such differences may be important for understanding the potential role of individual species in the transmission and maintenance of LPAI viruses and may have implications for improving sampling strategies for LPAI detection. Additional comparative studies, which include LPAI viruses originating from non-mallard species, are necessary to further characterize these infections in wild avian species other than mallards and provide a mechanism to explain these differences in viral excretion.

• Pathology in practice. Scuticociliatosis.

  Authors: Steven V Kubiski, Elizabeth W Howerth, Tonya M Clauss, Aimee L Berliner, Alvin C Camus

  Journal of the American Veterinary Medical Association. 02/2011; 238(3):301-3.

• Pathology in practice. Bovine lymphoma.

  Authors: Marion W Campbell, Elizabeth A Driskell, Brett S Tennent-Brown, Jennifer R Mayer, Elizabeth W Howerth

  Journal of the American Veterinary Medical Association. 01/2011; 238(1):47-9.

• Pathology in practice. Cutaneous mycobacteriosis.

  Authors: Victoria B Wilson, Raquel R Rech, Michaela G Austel, Cynthia L Bauer, Kenneth S Latimer, Susan Sanchez, Elizabeth W Howerth

  Journal of the American Veterinary Medical Association. 01/2011; 238(2):171-3.

• Homo- and heterosubtypic low pathogenic avian influenza exposure on H5N1 highly pathogenic avian influenza virus infection in wood ducks (Aix sponsa).

  Authors: Taiana P Costa, Justin D Brown, Elizabeth W Howerth, David E Stallknecht, David E Swayne

  PloS one. 01/2011; 6(1):e15987.

  Wild birds in the Orders Anseriformes and Charadriiformes are the natural reservoirs for avian influenza (AI) viruses. Although they are often infected with multiple AI viruses, the significance andWild birds in the Orders Anseriformes and Charadriiformes are the natural reservoirs for avian influenza (AI) viruses. Although they are often infected with multiple AI viruses, the significance and extent of acquired immunity in these populations is not understood. Pre-existing immunity to AI virus has been shown to modulate the outcome of a highly pathogenic avian influenza (HPAI) virus infection in multiple domestic avian species, but few studies have addressed this effect in wild birds. In this study, the effect of pre-exposure to homosubtypic (homologous hemagglutinin) and heterosubtypic (heterologous hemagglutinin) low pathogenic avian influenza (LPAI) viruses on the outcome of a H5N1 HPAI virus infection in wood ducks (Aix sponsa) was evaluated. Pre-exposure of wood ducks to different LPAI viruses did not prevent infection with H5N1 HPAI virus, but did increase survival associated with H5N1 HPAI virus infection. The magnitude of this effect on the outcome of the H5N1 HPAI virus infection varied between different LPAI viruses, and was associated both with efficiency of LPAI viral replication in wood ducks and the development of a detectable humoral immune response. These observations suggest that in naturally occurring outbreaks of H5N1 HPAI, birds with pre-existing immunity to homologous hemagglutinin or neuraminidase subtypes of AI virus may either survive H5N1 HPAI virus infection or live longer than naïve birds and, consequently, could pose a greater risk for contributing to viral transmission and dissemination. The mechanisms responsible for this protection and/or the duration of this immunity remain unknown. The results of this study are important for surveillance efforts and help clarify epidemiological data from outbreaks of H5N1 HPAI virus in wild bird populations.

• Pathology in practice. Morphologic diagnosis: Uterine adenocarcinoma with metastasis to the lungs, diaphragm, spleen, mesentery, and cecum.

  Authors: Yandace K Brown, Susan Knowles, Christine V Fiorello, Melinda S Camus, Elizabeth W Howerth

  Journal of the American Veterinary Medical Association. 12/2010; 237(11):1257-9.

• Effect of a prior exposure to a low pathogenic avian influenza virus in the outcome of a heterosubtypic low pathogenic avian influenza infection in mallards (Anas platyrhynchos).

  Authors: Taiana P Costa, Justin D Brown, Elizabeth W Howerth, David E Stallknecht

  Avian diseases. 12/2010; 54(4):1286-91.

  Wild birds, particularly Anseriformes and Charadriiformes, are considered the natural reservoir of low pathogenic avian influenza (LPAI) viruses. The high prevalence and subtype diversity of avianWild birds, particularly Anseriformes and Charadriiformes, are considered the natural reservoir of low pathogenic avian influenza (LPAI) viruses. The high prevalence and subtype diversity of avian influenza viruses at premigrational staging areas provide the perfect opportunity for multiple exposures to different LPAI virus subtypes. Natural consecutive and concurrent infections of sentinel ducks with different LPAI virus subtypes have been reported. The protective immune response from different LPAI virus infections is not understood nor is the effect of such repeated exposures. This study experimentally evaluated the effect of a prior exposure to a LPAI virus on the outcome of a heterosubtypic LPAI virus infection in mallards (Anas platyrhynchos). The results of this investigation suggest that recent prior exposure to a LPAI virus may affect the outcome of a subsequent heterosubtypic LPAI infection in mallards by reducing the duration of cloacal and oropharyngeal viral shedding as well as the viral load excreted via the cloaca. Wild mallards are likely exposed to multiple subtypes of LPAI virus during the periods of peak viral circulation, and the results of this study suggest that the duration of viral shedding in subsequent exposures might be reduced.

• Apparent disappearance of Vesicular Stomatitis New Jersey Virus from Ossabaw Island, Georgia.

  Authors: Lindsay Fann Killmaster, David E Stallknecht, Elizabeth W Howerth, John K Moulton, Paul F Smith, Daniel G Mead

  Vector borne and zoonotic diseases (Larchmont, N.Y.). 10/2010; 11(5):559-65.

  Ossabaw Island, Georgia, is the only reported endemic focus of Vesicular Stomatitis New Jersey Virus (VSNJV) in the United States. Based on recent negative serologic results of white-tailed deer andOssabaw Island, Georgia, is the only reported endemic focus of Vesicular Stomatitis New Jersey Virus (VSNJV) in the United States. Based on recent negative serologic results of white-tailed deer and feral swine and the failure to isolate VSNJV from Lutzomyia shannoni, it appears that VSNJV is no longer present at this site. This apparent disappearance does not appear to be related to a change in L. shannoni habitat, specifically to the density of tree holes in the maritime and mixed hardwood forests. We believe that the disappearance of VSNJV from Ossabaw Island is directly related to a reduction in the feral swine population and a subsequent increase in the utilization of white-tailed deer by the known vector, L. shannoni.

• Pathology in practice. Hypertrophy of the tunica muscularis.

  Authors: Victoria E Watson, Raquel R Rech, Elizabeth W Howerth

  Journal of the American Veterinary Medical Association. 09/2010; 237(5):505-7.

• Pathology in practice. Diagnosis: Poliomyelitis with intraneuronal Negri bodies.

  Authors: Allison C Boone, Leonardo Susta, Raquel R Rech, Rachel C Steffens, Elizabeth W Howerth

  Journal of the American Veterinary Medical Association. 08/2010; 237(3):277-9.

• Avian influenza virus isolates from wild birds replicate and cause disease in a mouse model of infection.

  Authors: Elizabeth A Driskell, Cheryl A Jones, David E Stallknecht, Elizabeth W Howerth, S Mark Tompkins

  Virology. 04/2010; 399(2):280-9.

  The direct transmission of highly pathogenic avian influenza (HPAI) viruses to humans in Eurasia and subsequent disease has sparked research efforts leading to better understanding of HPAI virusThe direct transmission of highly pathogenic avian influenza (HPAI) viruses to humans in Eurasia and subsequent disease has sparked research efforts leading to better understanding of HPAI virus transmission and pathogenicity in mammals. There has been minimal focus on examining the capacity of circulating low pathogenic wild bird avian influenza viruses to infect mammals. We have utilized a mouse model for influenza virus infection to examine 28 North American wild bird avian influenza virus isolates that include the hemagglutinin subtypes H2, H3, H4, H6, H7, and H11. We demonstrate that many wild bird avian influenza viruses of several different hemagglutinin types replicate in this mouse model without adaptation and induce histopathologic lesions similar to other influenza virus infections but cause minimal morbidity. These findings demonstrate the potential of wild avian influenza viruses to directly infect mice without prior adaptation and support their potential role in emergence of pandemic influenza.

• Pathology in practice. Proventricular dilatation disease.

  Authors: Sarah A Collette, Rita McManamon, Raquel R Rech, Elizabeth W Howerth

  Journal of the American Veterinary Medical Association. 03/2010; 236(5):519-21.

• Pathology in practice. Necrotizing pyogranulomatous meningoencephalitis with intralesional fungal hyphae, consistent with Cladophialophora bantiana.

  Authors: Jessica K Simmons, Rita McManamon, Raquel R Rech, Ashley E Phillips, Elizabeth W Howerth

  Journal of the American Veterinary Medical Association. 02/2010; 236(3):295-7.

• Pathology in practice. Disseminated aspergillosis.

  Authors: Joanna J Perry, Raquel R Rech, Melinda S Camus, Elizabeth W Howerth

  Journal of the American Veterinary Medical Association. 01/2010; 236(2):173-5.

• Mechanical transmission of vesicular stomatitis New Jersey virus by Simulium vittatum (Diptera: Simuliidae) to domestic swine (Sus scrofa).

  Authors: Paul F Smith, Elizabeth W Howerth, Deborah Carter, Elmer W Gray, Raymond Noblet, Daniel G Mead

  Journal of medical entomology. 11/2009; 46(6):1537-40.

  Biting flies have been suggested as mechanical vectors of vesicular stomatitis New Jersey Virus (family Rhabdoviridae, genus Vesiculovirus, VSNJV) in livestock populations during epidemic outbreaksBiting flies have been suggested as mechanical vectors of vesicular stomatitis New Jersey Virus (family Rhabdoviridae, genus Vesiculovirus, VSNJV) in livestock populations during epidemic outbreaks in the western United States. We conducted a proof-of-concept study to determine whether biting flies could mechanically transmit VSNJV to livestock by using a black fly, Simulium vittatum Zetterstedt (Diptera: Simuliidae), domestic swine, Sus scrofa L., model. Black flies mechanically transmitted VSNJV to a naive host after interrupted feeding on a vesicular lesion on a previously infected host. Transmission resulted in clinical disease in the naïve host. This is the first demonstration of mechanical transmission of VSNJV to livestock by insects.