10 Oct 2016
Alex Gough also looks at studies into <em>Giardia duodenalis</em> in dogs, discospondylitis, a cisplatin delivery platform and the intrathecal administration of cytosine arabinoside in his latest Research Review.
Alex Gough
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Canine influenza is a highly contagious, newly emerging pathogen of dogs, caused by variants of the influenza A virus – it has been reported in a number of countries, including the US.
In a retrospective case series, Secrest and Sharma1 described the thoracic radiographic characteristics of six dogs affected with canine influenza virus. They found the radiographic signs to vary, but five cases had unstructured interstitial and alveolar patterns. Cranioventral distribution was most common. One case had a mild pleural effusion. Intrathoracic lymphadenopathy was not noted.
The authors suggested canine influenza virus is considered as a differential diagnosis when patients present with respiratory signs and this pattern of radiographic changes.
Giardia duodenalis is an enteric parasite that can cause gastrointestinal signs in dogs. Saleh et al2 performed a prospective evaluation study to develop and evaluate a protocol to control this disease in a group of dogs housed together at a veterinary college.
Thirty-four dogs were included in the study and all were tested for Giardia.
They were then treated with fenbendazole daily for 10 days. On the fifth day, the dogs were bathed and moved to new, clean, disinfected accommodation, during which time their normal accommodation was disinfected and dried. After this, the dogs were returned to their original kennels.
Weekly faecal samples were collected until day 41 and then 3 weekly samples until day 209.
Before treatment, all dogs were shedding Giardia cysts. In subsequent follow-up testing, only one cyst was detected, on day 20.
The authors concluded the protocol successfully controlled Giardia infection in this colony. They also noted DNA sequencing of the organism confirmed it was a type normally found in dogs and not people, making zoonotic transmission less likely.
Discospondylitis is an infection of the vertebral column, often caused by haematogenous spread of bacteria.
In a retrospective case series of 10 dogs less than six months old, Kirberger3 described the early diagnostic imaging findings of the condition.
The dogs were all examined for vertebral pain less than three weeks after a trauma, bite wound or systemic illness. The earliest change noted on radiography was a narrowed intervertebral disc space and this change was found in 28 disc spaces.
Subluxation of vertebrae was also found in 8 of the 28 affected discs. Vertebral end plate lysis occurred later in the course of the disease and was observed on follow-up radiographs.
Five dogs underwent ultrasound examination, which showed ventrally bulging hypoechoic material at affected disc sites, as well as loss of reverberation artefact in four cases – in two cases this was found prior to radiographic changes.
Four dogs underwent CT and three of these had changes noted prior to changes on x-ray.
The author notes young dogs with discospondylitis had atypical early imaging findings compared to adult dogs.
Hyaluronan-cisplatin (HA-Pt) nanoconjugate is a drug delivery platform allowing sustained release of cisplatin locally or regionally. Cai et al4 prepared the drug and tested it in 18 healthy rats, 9 healthy mice and 16 dogs with cancer. The dogs were given one to four injections into or around the tumour, at intervals of three weeks. Blood tests for pharmacokinetic analysis, full blood count and renal parameters were taken, as well as urinalysis, before, and one week after, each treatment. No adverse effects were found in the initial tests on rodents. Seven out of 16 dogs with cancer completed the study. Three were considered to have a complete tumour response, three had stable disease and one had progressive disease. However, myelosuppression was noted in six dogs and cardiotoxicosis in two dogs.
The authors concluded HA-Pt treatment results positively in dogs with cancer, especially those with squamous cell carcinoma.
Unfortunately, the rate of adverse effects were high, but the study could have implications for developing similar treatment in humans.
Traditional Chinese herbal medicine is used in the treatment of a variety of conditions, but the evidence for efficacy of most of the treatments is weak to non-existent.
Wirth et al5 performed a study into the effects of Yunnan Baiyao, a Chinese herbal medicine thought to have use as an anti-inflammatory and analgesic and to aid haemostasis and wound healing.
An in vitro investigation was performed testing the activity of Yunnan Baiyao against three canine hemangiosarcoma cell lines. The authors found the treatment caused a dose and time-dependent apoptosis and recommended further studies of the treatment. However, it should be noted many things will kill cancer cells in vitro, which do not translate to viable in vivo treatments.
Meningoencephalitis of unknown origin is a challenging disease to treat – often requiring large doses of immunosuppressive drugs, which have the potential for adverse effects.
One way to deliver immunosuppressive drugs direct to the area of inflammation is with intrathecal administration.
Genoni et al6 performed a study to assess the safety of intrathecal administration of cytarabine with or without methotrexate.
A total of 112 dogs and eight cats with suspected inflammatory or neoplastic disease of the CNS were treated with intrathecal cytosine arabinoside, and some of these cases were also given intrathecal methotrexate. One patient experienced a generalised seizure shortly after recovery from anaesthesia, which was controlled with diazepam.
The authors concluded intrathecal administration of cytosine arabinoside, with or without methotrexate, is a safe procedure in dogs and cats.
Lactate measurements are often used in critical care settings to help evaluate prognosis and to assess response to treatment – for example, fluid therapy.
Redavid et al7 performed a prospective observational study of 123 cats to evaluate the incidence of hyperlactataemia in sick cats that had been hospitalised for emergency treatment and also to assess whether serial lactate measurements has any prognostic usefulness. A total of 23% of cats had increased lactate levels at admission. However, neither the lactate concentration at admission or serial lactate measurements were found to relate to prognosis as measured by survival to discharge – or to correlate with the duration of hospital stay.
The authors recommended further studies of lactate measurements in cats involve larger populations with more specifically defined diseases.
