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The Itchy Dog: An Overview of Diseases

November 6, 2013 Leave a comment

Chris Reeder, DVM, DACVD

Itchy Frenchie

Sometimes no matter how hard we try, a diagnosis of pruritic skin disease is frustrating.  There are a few key questions and findings that may make life a little easier in dealing with the itchy dog.  The skin as an organ has incredible powers. Not mystical or magical, those are confined to brain along with neurologic pathways to control motion and physiologic/psychologic processes. No, the skin has its own special powers.  It acts as a physical barrier providing innate protection against the evils of the environment.  Skin stretches and can transition from taut to lose, thick to thin, it controls water loss and temperature regulation, it acts as a sensory organ and to many animals, camouflage to help hide from predators or stalk prey.  Skin truly is an incredible organ, though as incredible as it is, an Achilles’ heel does exist…..pruritus.

Pruritus is derived from the Latin prurire meaning to “itch.”   It is defined as the desire or reflex to scratch.  Itching in the dog is one of the most common presenting complaints from owners to the general practitioner, yet one of the most frustrating and costly as well.  There is help, several key questions and findings may provide a starting point or diagnosis as to why a dog is itching.  Our first step is the question the owner about the dog’s condition:

–          Age of onset of the itching

–          Duration of the itching

–          Other animals in the household affected

–          Housed indoor, outdoor or both

–          Travel history

–          Current and previously fed diets (including human foods)

–          Seasonal history or exacerbations of itching

–          Previous medications, what worked and what didn’t work

–          Current flea/tick control products (other animals treated)

–          Number of bowel movements daily

–          Loose, runny stools or any vomiting

Many animals who have a food allergy will present as young dogs (<1 year of age) with loose or runny stools, >3 bowel movements daily and may be refractory to glucocorticoid use.  Other household animals are not affected and this is typically non-seasonal with itching as a constant feature.  Compare that to the typical dog with atopy (environmental allergies) and we see that most of those dogs present first between 1-4 years of age, have some seasonal pattern, respond to glucocorticoids with a reduction of pruritus and no other animals in the household are affected.  The author’s experience, along with many dermatologists, find that atopy is a much more common presentation than food allergy in roughly 90% to 10%, respectively.  We also see that food allergic dogs often have some compromise to the gastrointestinal barrier function.  This could be a history of intestinal parasites, Parvovirus enteritis, or any other disruption to the gut integrity.  What about a dog whose symptoms appears more atopic but is non-seasonal?  That could be a dog that is suffering from indoor allergens (dust mites, storage mites, human or cat dander, sheep wool, cotton, etc) which allergy testing may be a helpful tool in order to diagnose.

Scabies can mimic food allergy and atopy very closely.  Other animals or even humans in the household may be affected with pruritus.  The typical approach to dogs with scabies is to identify a pinnal-pedal reflex.  This involves grasping the pinna between the thumb and forefinger of both hands and rubbing the skin together.  A positive response would involve the ipsilateral hind leg start scratching vigorously after a few seconds.  It has been reported that up to 80% plus of dogs with scabies exhibit a positive pinnal-pedal response and these are cases to empirical treat with an acaracidal therapy (e.g. Advantage-multi® Bayer, Revolution® Pfizer) which is usually an off-label dosing of one treatment every 2 weeks for 3 total doses.  Common areas affected with scabies infestation include: hocks, elbows, pinnae, groin and scrotum.  All animals in the household should be treated as some may serve as a reservoir even if not itching.

Golden Butt Scratch

Flea allergy is truly a hypersensitivity response.  This appears as a dose-dependent phenomenon with the higher number of flea bites with salivary protein exposure thus resulting in an allergic response.  The number of bites to induce an allergic response varies with some animals showing no response even with hundreds of bites.  It is important to examine the dog, especially those with long coats, on the rump region.  A severe inflammatory response can be seen in dogs with a strong allergic response to fleas with moist pyoderma and excoriations predominantly over the dorsal lumbar region.  Another common finding in dogs with flea allergy is the discontinuation of flea control over the winter months.  Fleas overwinter indoors and continue to thrive, only at a slower rate than the warm and humid summer months.  Continued flea control for all animals in the household is a very effective means of controlling flea allergies.  Several topical formulations now have both flea prevention and heartworm prevention in a single dose application (e.g. Advantage-multi® Bayer).  Bathing around the time of application of the topical spot-on formulations of flea preventative is another question to ask the owner.  Typical recommendations are to wait 48-72 hours after application to bathe a dog or use an oral flea preventative (e.g. Comfortis® or Trifexis® Elanco).

Ringworm, is neither a ring nor a worm, the saying goes “if it looks like ringworm, it’s probably not” in dogs holds true.  Dermatophytosis in dogs usually presents with pruritus, hair loss, erythema and scaling.  Rarely does ringworm present as focal, circular patches of alopecia in dogs.  Various forms of ringworm can be present in dogs, geophilic, zoophilic, anthrophilic with the geophilic (soil) or zoophilic (animal) forms most common.  Microsporum gypseum is a geophilic dermatophyte whereas Microsporum canis is a zoophilic dermatophyte and the most common species seen in the dog and cat.  Occasionally multiple animals in the household may be affected and about 10% of humans can also have lesions which are typically pruritic.  A dermatophyte test media (DTM) culture is ideal to diagnose and speciate the type of dermatophyte present.  Fluconazole (5-10 mg/kg po daily) is the author’s treatment of choice for dermatophytosis.  Terbinafine (Lamasil®, 30-40 mg/kg po daily) may also be used for refractory cases.

Pruritus also damages the cutaneous barrier function both as, what we think is, a genetic dysfunction of the intercellular cement along with direct excoriations of the integument. This barrier defect has led to the development of many good products to help control and restore function.  Wipes, shampoos, lotions, balms and sprays have all been recently developed an are on the maket to help restore or improve skin barrier function in animals.  Shampoos have technology to even prevent bacteria/yeast from adhering to the skin surface (Virbac glycotechnology).  Pro-ceramides have been incorporated into sprays and shampoos to help repair damaged skin (phytosphingosine, Douxo® (Sogeval)).

Pruritus may have developed due to an allergic response to food, parasites or the environment and taking the time and understanding what to look for in these cases can make for a much more rewarding treatment outcome.  Many dogs need ongoing management for their atopy, need to be on flea prevention every 3-4 weeks ongoing or must be maintained on certain diets if food allergic.  Scabies is curable, though we do occasional see reservoirs in other household dogs or wildlife making further questioning an important part of the treatment.  Asking the right questions along with a thorough history and physical exam may help increase the correct diagnosis and decrease frustrations levels for the itchy dog.

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PREGNANCY DIAGNOSIS AND TIMING ELECTIVE C-SECTIONS

January 6, 2012 Leave a comment

C. Scott Bailey, DVM, MS, DACT

Consultant, Veterinary Answers

Veterinarians are often asked to perform pregnancy diagnosis and time a c-section with very little information from the owner. Often, the only information provided is the breeding-dates and occasionally even those are hard to come by. Consequently there is a need for veterinarians to be familiar different with methods of estimating gestational age. This is particularly important when an elective caesarean section is desirable. Elective c-sections can carry an excellent prognosis for maternal and fetal viability when timed correctly and may be less stressful to the bitch, puppies and attending veterinarian than waiting for a potential dystocia. Animals that are particularly good candidates are those with a history of dystocia or a c-section and animals that have small (less than 3 pups) or large (more than 8 pups) litter sizes. Dogs of certain breeds have a known predisposition to dystocia, such as Boxers, Bulldogs, Scottish Terriers, Great Danes and Bernese Mountain Dogs [1].

A number of factors play critical roles in the ultimate success-rate of elective c-sections, including fetal maturity, patient preparation, selection of anesthesia protocol and surgical technique as well as neonatal care of the pups. In this review we focus on only the first of these – Timing of c-section to maximize fetal maturity.

Three basic methods exist to predict parturition in the bitch:

Hormonal Assay

While the easiest methods for timing involve breeding management, breeding dates provided by owners are notoriously unreliable. Parturition may occur anywhere from 57 to 72 days after a single observed breeding [2]. On the contrary, the easiest and most accurate way to predict whelping is to diagnose or estimate the time of LH surge. Bitches reliably whelp 64-66 days post LH surge [2,3], which can be diagnosed by repeated LH assay (every 12 hours due to the short duration of the LH surge in the bitch). LH-peak may also be estimated by observing serum progesterone levels that achieve 2-3ng/ml and continue to rise thereafter [3,8]. Shortly after this period, vaginal cytology may be used to diagnose the onset of diestrus, occurring approximately 51-60 days before whelping [4].

Thereafter a variety of measures represent guides to estimate gestational stage within 2-3 days [4-6]. Further, equations have been developed to calculate gestational age in a variety of breeds [6,7].

A brief summary of useful ultrasonographic and radiographic markers of gestational age is listed below:

Ultrasonographic examination [5-8]

The fetal heartbeat is visible at approximately 22-26 days.

Limbuds, fetal movement and a fluid filled stomach may be seen on day 29, 30 and 33.

Fetal length exceeds chorionic width at approximately day 42.

Radiographic examination [5,7,9]

Pregnancy can first be reliably diagnosed radiographically day 45-48 post LH surge. More specific information is also available describing the appearance of specific structures in relation to whelping.

The scapula, humerus and femur are first detectable 17 days (15-18) prepartum.

The pelvis and 13 pairs of ribs are visible 11 days (9-13) prepartum.

Teeth are visible 4 days (3-8) prepartum.

During the final days of gestation, cortisol is produced and released from the maturing fetal adrenal gland in response to space-constraint and other physiologic stressors. This results in production of prostaglandin F2α in the placenta and endometrium, which in turn induces luteolysis and starts the cascade of events that ultimately result in fetal expulsion [10]. At the same time the cortisol also has critical effects on the fetus, resulting in rapid maturation of vital organ systems, including the musculoskeletal system, gastrointestinal system and lungs. Prior to these final maturation processes, puppy survival may be decreased due to weakness, poor mobility and respiratory distress after removal from the uterus. On the contrary, if these processes have occurred and the bitch experiences a dystocia, survival may also be decreased. Consequently, the goal of gestational timing should be to predict whelping accurately enough to intervene after final maturation has occurred but before the bitch is in active labor. To do this, repeated monitoring of hormone levels during the final week of gestation, in combination with fetal monitoring via ultrasound or tocometry, may improve fetal viability and prevent dystocias [11-13].

Progesterone [11]:

Progesterone measures below 2ng/ml indicate imminent parturition within 18-36 hours.

A temperature drop by 1-3F from previous measures occurs in 75-85% of bitches within 8-18 hours prior to parturition.

Fetal heart-rate can accurately diagnose fetal distress during late gestation [12,13]

Normal late pregnancy: 200 beats/min

Fetal Stress: 180 beats/min – Values in this range indicate readiness for parturition

Fetal distress: 150 beats/min – values of 150 or below indicate the urgent need for emergency intervention to save the puppy.

References:

1) Bergström A, Nødtvedt A, Lagerstedt AS, Egenvall A. Incidence and breed predilection for dystocia and risk factors for cesarean section in a Swedish population of insured dogs. Vet Surg 2006 Dec;35(8):786-91.

2) Concannon PW, Whaley S, Leid D, Wissler R. Canine Gestation length: vacioation related to time of mating and fertile life of sperm. Am J Vet Res 1983;44:1819-21.

3) Cohen JA, Holle DM, Meyers-Wallen VN. Accuracy of canine parturition date prediction from LH peak. Clin Theriogenology 2009;1:570

4) Holst PA, Phemister RD. Onset of diestrus in the Beagle bitch: definition and significance. Am J Vet Res 1974;35:401-6

5) Aissi A and Slimani C. Ultrasonographic appearance of the gestational structures throughout pregnancy in bitches. Am J Anim Vet Sciences 2008;3(1):32-35

6) Yeager AE  and Concannon PW. Association between preovulatory LH surge and the early ultrasonographic detection of pregnancy and fetal hearteats in beagle dogs. Theriogenology 1990;34:655-665.

7) Lopate C. Estimation of gestational age and assessment of canine fetal marutation using radiology and ultrasonography: A review. Theriogenology 2008;70:397-402

8) Luvoni GC and Beccaglia M. The Prediction of Parturition Date in Canine Pregnancy. Reprod Dom Anim 2006;41:27-32.

9) Rendano VT. Radiographic evaluation of fetal development in the bitch and fetal death in the bitch and queen. In: Current veterinary therapy vol VIII. WB Saunders Co 1983; 947-52

10) Concannon PW, Butler WR, Hansel W, Knight PJ, Hamilton JM. Parturition and lactation in the bitch: serum progesterone, cortisol and prolactin. Biol Reprod 1978 Dec;19(5):1113-8.

11) Verstegen-Onclin K, Verstegen J. Endocrinology if pregnancy in the dog: A review. Theriogenology 2008;70:291-199.

12) Verstegen JP, Silvia LDM, Onclin K, Donnay I. Echocardiographic study of heart rate in dog and cat fetuses in utero. J Reprod Fertil Suppl 1993;47:174-80

13) Zone MA and Wanke MM. Diagnosis of canine fetal death by ultrasonography J. Reprod Fertil 2001;57:215-9.

Cool Recent Abstracts

April 30, 2009 Leave a comment

SMALL ANIMAL

Intracranial Arachnoid Cysts in Dogs

from Compendium by Curtis W. Dewey – Veterinary Answers Consultant, Peter V. Scrivani, Ursula Krotscheck, Sofia Cerda-Gonzalez, Kerry Smith Bailey, Dominic J. Marino

Intracranial arachnoid cyst (IAC) is an infrequently reported developmental disorder seen primarily in small-breed dogs. It usually occurs in the caudal fossa, in the region of the quadrigeminal cistern. Although still considered uncommon, IAC is being recognized more frequently in veterinary medicine, coinciding with the increased availability of magnetic resonance imaging. In this article, clinical information from previously reported cases of canine IAC is combined with additional case information from our hospitals. Similar to IAC in people, it is thought that canine IAC is often an incidental finding. When IAC is responsible for neurologic disease in dogs, generalized seizures and cerebellovestibular dysfunction are the most common clinical presentations. Medical therapy of IAC focuses on management of increased intracranial pressure and seizures, if the latter are part of the clinical complaints. Surgical therapy of IAC involves either cyst fenestration or shunting the excess fluid to the peritoneal cavity.

Peripheral Nucleated Red Blood Cells as a Prognostic Indicator in Heatstroke in Dogs

from JVIM by I. Aroch, G. Segev, E. Loeb, Y. Bruchim

Heatstroke in dogs is often fatal and is associated with a high prevalence of secondary complications. Peripheral nucleated red blood cells (NRBC) occur in dogs with heatstroke, but their association with complications and the outcome is unclear. Peripheral NRBC are common in dogs with heatstroke and have prognostic significance. Forty client-owned dogs with naturally occurring heatstroke. Prospective, observational study. Dogs were followed from presentation to discharge or death. Serum biochemistry and coagulation tests were performed at presentation. CBC and evaluation of peripheral blood smears were performed at presentation and every 12 hours. The relative and the absolute NRBC numbers were calculated. Presence of NRBC was observed in 36/40 (90%) of the dogs at presentation. Median relative and absolute NRBC were 24 cells/100 leukocytes (range 0[ndash]124) and 1.48 × 103/[mu]L (range 0.0[ndash]19.6 × 103/[mu]L), respectively. Both were significantly higher in nonsurvivors (22) versus survivors (18) and in dogs with secondary renal failure and DIC versus those without these complications. Receiver operator curve analysis of relative NRBC at presentation as a predictor of death had an area under curve of 0.92. A cut-off point of 18 NRBC/100 leukocytes corresponded to a sensitivity and specificity of 91 and 88% for death. Relative and absolute numbers of peripheral NRBC are clinically useful, correlate with the secondary complications, and are sensitive and specific markers of death in dogs with heatstroke, although they should never be used as a sole prognostic indicator nor should they replace clinical assessment.


Relationships between Low Serum Cobalamin Concentrations and Methlymalonic Acidemia in Cats

from JVIM by C. G. Ruaux, J. M. Steiner, D. A. Williams

Serum cobalamin concentrations below reference range are a common consequence of gastrointestinal disease in cats. Serum cobalamin [le] 100 ng/L is associated with methylmalonic acidemia. To determine the prevalence of cobalamin deficiency, defined by elevated serum methylmalonic acid (MMA), in cats with serum cobalamin [le] 290 ng/L, and the optimum serum cobalamin concentration to predict cobalamin deficiency in cats. Residual serum samples (n = 206) from cats with serum cobalamin [le] 290 ng/L. Retrospective, observational study. Serum cobalamin and folate were measured with automated assays. Serum MMA was determined by gas chromatography-mass spectrometry. Cobalamin deficiency was defined as serum MMA > 867 nmol/L. Sensitivity and specificity of serum cobalamin concentrations [le]290 ng/L for detecting MMA > 867 nmol/L were analyzed using a receiver-operator characteristic curve. There was a negative correlation between serum cobalamin and MMA concentrations (Spearman’s r=[minus]0.74, P 867 nmol/L. No significant difference in serum folate concentrations was detected between affected and unaffected cats. Elevated MMA concentrations, suggesting cobalamin deficiency, are common in cats with serum cobalamin [le] 290 ng/L. Cobalamin deficiency is clinically significant, and supplementation with parenteral cobalamin is recommended for cats with gastrointestinal disease and low serum cobalamin concentrations.

For more on MMA in human beings, click here.

Small Mammals
Single- and multiple-dose pharmacokinetics of marbofloxacin after oral administration to rabbits

From AJVR by James W. Carpenter, MS, DVM; Christal G. Pollock, DVM (VETERINARY ANSWERS CONSULTANT); David E. Koch, MS; Robert P. Hunter, PhD

Objective—To determine the pharmacokinetics of marbofloxacin after oral administration every 24 hours to rabbits during a 10-day period.

Animals—8 healthy 9-month-old female New Zealand White rabbits.

Procedures—Marbofloxacin (5 mg/kg) was administered orally every 24 hours to 8 rabbits for 10 days. The first day of administration was designated as day 1. Blood samples were obtained at 0, 0.17, 0.33, 0.5, 0.75, 1, 1.5, 2, 3, 4, 5, 6, 8, 12, and 24 hours on days 1 and 10 of marbofloxacin administration. Plasma marbofloxacin concentrations were quantitated by use of a validated liquid chromatography–mass spectrometry assay. Pharmacokinetic analysis of marbofloxacin was analyzed via noncompartmental methods.

Results—After oral administration, mean ± SD area under the curve was 10.50 ± 2.00 μg·h/mL and 10.90 ± 2.45 μg·h/mL, maximum plasma concentration was 1.73 ± 0.35 μg/mL and 2.56 ± 0.71 μg/mL, and harmonic mean terminal half-life was 8.0 hours and 3.9 hours for days 0 and 10, respectively.

Conclusions and Clinical Relevance—Marbofloxacin administered orally every 24 hours for 10 days appeared to be absorbed well and tolerated by rabbits. Administration of marbofloxacin at a dosage of 5 mg/kg, PO, every 24 hours is recommended for rabbits to control infections attributable to susceptible bacteria.

EQUINE
Risk Factors for Equine Postoperative Ileus and Effectiveness of Prophylactic Lidocaine

from JVIM by S. Torfs, C. Delesalle, J. Dewulf, L. Devisscher, P. Deprez
Postoperative ileus (POI) is a frequent and often fatal complication of colic surgery. Reliably effective treatments are not available. To determine risk factors and protective factors associated with POI, and to assess the effect of lidocaine IV on short-term survival. One hundred and twenty-six horses that underwent small intestinal colic surgery and that survived for at least 24 hours postoperatively. Retrospective cross-sectional study. The association of 31 pre-, intra-, and postoperative variables with POI and the association of lidocaine treatment with short-term survival were investigated. Associations were evaluated with univariable logistic regression models, followed by multivariable analysis. Significant associations of high heart rate (odds ratio [OR] = 1.05, 95% confidence interval [CI] 1.03[ndash]1.08), the presence of more than 8 L of reflux at admission (OR = 3.02, 95% CI 1.13[ndash]8.02) and the performance of a small intestinal resection (OR = 2.46, 95% CI 1.15[ndash]5.27) with an increased probability of POI were demonstrated. Prophylactic lidocaine treatment was significantly associated with a reduced incidence of POI (OR = 0.25, 95% CI 0.11[ndash]0.56). Lidocaine treatment was also significantly associated with enhanced short-term survival (OR = 0.30, 95% CI 0.09[ndash]0.98). The variables associated with an increased risk of POI can be useful in identifying horses at risk of POI and in providing a more accurate prognosis. The results are supportive for lidocaine IV as an effective prokinetic treatment after small intestinal colic surgery.