Update on Echinococcus multilocularis in Ontario
Emily Brouwer, Andrew Peregrine, Andrew Vince
In the March 2013 issue of the AHL Newsletter, Dr. Brooks et al. described a case of hepatic Echinococcus multilocularis infestation in a 2-year-old Boxer dog. Since that time, 3 additional cases have been identified in dogs by the OVC Department of Pathobiology and the Animal Health Laboratory from within Southern Ontario, a region in which this pathogen had not been previously identified.
Very recently, a 4-year-old male castrated Boxer dog was presented to the OVC Health Sciences Center with lethargy, vomiting, abdominal pain, and radiographic findings of a cranial abdominal mass. Clinical pathology on admission included severe leukopenia, neutropenia, and mild lymphocytosis. Analysis of free abdominal fluid revealed septic suppurative inflammation. On exploratory laparotomy, 3 large cavitated masses were identified in the liver varying from 10-25cm in diameter; 2 were amenable to surgical excision and submitted for histopathology (Fig. 1). These masses were filled with tan purulent fluid and had coalescing white nodules within their wall; histologically, the wall of each mass contained a mix of granulomatous and neutrophilic inflammation surrounding multilocular cysts lined by PAS-positive hyaline membranes, and occasionally contained calcareous corpuscles and cross sections of protoscolices (Fig. 2). The diagnosis of Echinococcus multilocularis was confirmed using PCR and sequencing at the Institut für Parasitologie in Bern, Switzerland.
Overall, 3 cases of abdominal visceral and 1 case of subcutaneous Echinococcus multilocularis infestation have been identified recently in Ontario dogs, comprising 3 Boxer dogs and 1 Leonberger. Only one case had a history of travel outside of Ontario. Visceral infestations are uncommon in canids, which are typically definitive hosts with infestations limited to the intestinal tract; visceral infestations typically result from ingestion of large numbers of parasite eggs, most likely in the feces of wild canids. Because of the tendency to produce multifocal and often dramatic masses, alveolar echinococcosis should be considered a differential diagnosis for intraabdominal neoplasia in dogs.
This pathogen is of significant public health interest, as Swiss studies have demonstrated that approximately one-third of canine visceral cases also have enteric infections; as such, it is considered likely that more cases will be seen in Ontario. Canine enteric infections are potentially infectious to humans in close contact; human cases are typically visceral, mimic neoplasia, and have a high case fatality if not treated (particularly when diagnosed late). Dogs and people in contact with infected dogs are typically screened serologically for exposure.
Bayer Animal Health is funding an MSc research project beginning in September 2015, which will investigate levels of infestation within hunter-trapped foxes and coyotes (the typical definitive wildlife hosts for this parasite) across southern Ontario.
For additional information on this parasite, a YouTube video presentation by Dr. Andrew Peregrine is available at: https://www.youtube.com/watch?v=XSss8BaD7Lg&feature=youtu.be
Figure 1. Intraoperative photograph of liver masses with characteristic military pale surface nodules (Dr. Tom Gibson, Ontario Veterinary College, with permission).
Figure 2. Histology from the wall of one of the resected masses, with two protoscolices from encysted tapeworms (H&E, 400x magnification).
Minimal inhibitory concentration (MIC) of minocycline in treatment of Staphylococcus pseudintermedius
The AHL has been reporting minimal inhibitory concentration (MIC) for minocycline for all methicillin-resistant Staphylococcus pseudintermedius (MRSP) isolates. Although minocycline has not been officially approved for use in dogs, it can be a good alternative in treating multidrug resistant (MDR) MRSP. Maaland et al. determined pharmacokinetic and pharmacodynamic data for minocycline in dogs. Minocycline, when used twice daily at the dosage of 5 mg/kg, will inhibit growth of S. pseudintermedius isolates with MIC values of ≤0.25 μg/mL. Furthermore, it has been shown that S. pseudintermedius isolates with MIC ≤0.25 μg/mL do not carry any currently known tetracycline resistance genes, unlike their counterparts with MIC values above 0.25 μg/mL.
“Urinalysis is one of the most important diagnostic tools available to veterinarians.” (Dr. Carl Osborne, Urinalysis: A clinical guide to compassionate patient care)
Without information obtained by a comprehensive urinalysis (which includes dipstick, specific gravity, and sediment examination), many of the changes noted on serum biochemistry profiles or clinical assessment cannot be adequately interpreted. For example, urine specific gravity is helpful in differentiating the cause of azotemia, urinary protein loss may account for documented hypoproteinemia, and hyposthenuria may be related to an underlying urinary tract infection, etc.
Even the absence of significant findings is helpful, providing the veterinarian with objective information with which to exclude certain disease processes. As such, a urine sample should be part of the minimum data base, evaluated alongside every serum biochemistry profile and CBC, whenever it is clinically possible.
In order to maximize the information obtained from urinalysis, a standard protocol should be established, keeping the following points in mind:
* Perform the urinalysis when urine is at body or room temperature. If urinalysis cannot be performed within approximately 30-60 minutes of sample collection, refrigeration is indicated. While some things are best when cold and straight from the fridge, urine is not one of these!
* Enzyme-based tests such as glucose oxidase, require urine to be at room temperature.
* The specific gravity of urine is higher in cold urine than warm.
* Precipitated substances are more likely to re-dissolve in samples that have been rewarmed.
* Determine urine specific gravity using a veterinary specific refractometer.
* Keep the urine dipstick container cap on tightly, ensure that the desiccant is in place, and store the container away from moisture, direct sunlight, heat, acids, alkalis, and volatile fumes. Do not use outdated reagents. Commercially available control material (e.g., Dipper Quantimetrix Corp) is available to check dipstick quality.
* Do not interpret the nitrite, leukocyte, or specific gravity pads, these are not reliable in animal species.
* Minimize contamination of reagents from one test pad with reagents from an adjacent test pad by keeping the reagent strips horizontal after the application of urine.
* Evaluate the test results at the times specified by the manufacturer.
Do examine a urine sediment preparation. If using a sediment stain, periodically examine the stain itself to ensure that is has not become contaminated by bacteria or yeast.