MALIGNANT TUMOURS IN LABRADOR RETRIEVERS USED FOR NARCOTIC DETECTION

Th e two corpses of police dogs, of Labrador retriever breed used for fi nding narcotics, were sent to the Scientifi c Veterinary Institute “Novi Sad”, and examined post-mortem, in order to determine the cause of death. Post-mortem examination revealed the presence of neoplastic changes in the mandibular region, pulmonary parenchyma and axillary region. Th e samples of neoplastic changes were sent to the Laboratory of Patohistology within the Faculty of Veterinary Medicine, University of Belgrade, in order to specify the diagnosis. Histopathology examination revealed an adenocarcinoma in lungs and haemangioendothelioma in axillary region. Is there any role of drug sniffi ng on the occurrence of neoplasia in Labrador retriever breed is still unknown, but it could be an important factor in the development of neoplasia in these dogs.


INTRODUCTION
Labrador retriever dogs are oft en used as sniff er dogs -they are trained by a large number of law enforcement agencies and rescue teams worldwide. Th ese dogs are able to detect the scents of illegal drugs, explosives, fl ammable materials, and other contraband items such as illegal imports of ivory (Oesterhelweg et al., 2008). Drug-sniffi ng dogs may be exposed to illicit drugs and other toxic agents in the line of duty, most commonly through inhalation and ingestion. Ingestion is the most common route of exposure. Th ey may ingest whole bags of drugs which must be removed surgically or via endoscopy to prevent rupture and massive exposure. Police dogs may be at increased risk for malicious poisonings (Gupta R., 2012). Inhalation exposures are generally of lesser magnitude but may result in a more rapid onset of action of the agent (Llera and Volmer, 2006). When compared to the pet population, police dogs had a higher risk of developing neoplasms (Kippens and Grondalen, 1999). Th is case presentation describes the presence of malignant tumours in two police dogs, Labrador retriever breed trained for fi nding drugs.

CASE PRESENTATION
During 2015 and 2016, two corpses of offi cial police dogs used for drug detection were brought to the Scientifi c Veterinary Institute ``Novi Sad`` to determine the cause of death. Th e necropsy was performed at the autopsy hall of the Scientifi c Veterinary Institute ``Novi Sad``. Th e fi rst dog was a 12-yearsold male Labrador retriever weighing around 40 kg. Th e second dog was a 15-years-old male Labrador retriever weighing approximately 50 kg. Both dogs were non-neutered dogs, older than 10 years and in very poor body condition. Th ey were short hair yellow dogs. Both dogs were found dead in police rooms intended for the accommodation of service dogs. Th ere were no data regarding a previous treatment of dogs.
During external post-mortem examination of the fi rst dog, in the area of mandibular region globular formation of hard consistency was observed. Th is neoplastic change was 2x2cm in diameter, while the surrounding tissue was oedematous, haemorrhagic, jelly-like consistency. Th e left lung was enlarged, and during palpation of the lung parenchyma, neoplastic change 5x3cm in diameter was detected (Figure 1-A). Th is neoplastic change was hard consistency. On cross-section of the left lung, sticky dark red liquid was observed ( Figure 1 Aft er necropsy and tissue sampling, the samples were sent to the Laboratory for Patohistology, at the Faculty of Veterinary Medicine, University of Belgrade in order to specify the diagnosis. For patohistological analysis, the sample was fi xed in 10% neutral-buff ered formalin, embedded in paraffi n, and sections of 4 μm thickness were cut. Th ese sections were stained with haematoxylin and eosin (H&E). Histopathologically, a well-diff erentiated adenocarcinoma with squamous metaplasia was diagnosed at the left lung of 12-years-old dog. Microscopically, the neoplastic tissue of lungs showed mix of small basaloid cells and larger diff erentiated cells that were polygonal, with abundant glassy eosinophilic cytoplasm and prominent atypia of neoplastic cells. Acinar diff erentiation with formation of lumens was clearly evident, along with squamous diff erentiation of cells. Histopathological examination of neoplastic change of 15-years-old dog confi rmed Haemangioendothelioma of axillary region. Microscopically, neoplastic tissue of axillary region had numerous irregular vascular channels and large areas of haemorrhage. Tumour cells were consisted of pleomorphic endothelial cells, ranging from spindle-shaped to polygonal to ovoid.

DISCUSSION
Malignant tumours are a common health problem in dogs worldwide. All dog breeds, as well as crossbred dogs may be aff ected, and it is notable that some purebred dogs appear to be at increased risk of certain types of malignant tumours, suggesting underlying genetic predisposition (Dobson, 2013).
Adenocarcinoma is a malignant tumour originating in the glandular and epithelial tissue (the lining of the internal organs). Th is type of malignant tumour growth can take place in many parts of the body. It commonly aff ects older dogs, usually more than six years of age. No particular breed is known to be predisposed and it is more common in male dogs than females. Th is type of tumours usually has a poor prognosis. Th e exact cause is still unknown. According to Scanziani  Haemangiosarcoma (HSA, malignant hemangioendothelioma), a malignant tumour of endothelial cells, occurs most frequently in old dogs, but is less common than haemangioma. Hemangiosarcoma is an aggressive and common cancer in dogs and it has been estimated to represent 7% of canine malignant tumours (Dobson, 2013). German shepherd dogs are most commonly aff ected, and some other breeds are over-represented. Hemangiosarcoma is a highly malignant tumour arising from blood vessels, probably less common than some of the other mesenchymal malignancies. Th e most common primary sites for hemangiosarcoma in dogs are visceral organs, notably the spleen and liver; it may also arise in the right atrial appendage. (Dobson, 2013). Metastasis most oft en occurs to the liver, omentum, mesentery, lungs either hematogenously or through transabdominal transplantation via seeding aft er tumour rupture. Most aff ected dogs die from acute internal haemorrhage secondary to rupture of the tumour. Despite surgical and chemotherapeutic management, the median survival time for dogs diagnosed with HSA is little more than 6 months (Hammer et al., 1991;Cliff ord et al., 2000;Sorenmo et al., 2000;Sabattini and Bettini, 2009). Th e breed that appears to be predisposed is the German shepherd dog, and other commonly reported breeds include the Golden retriever, Pointer, Boxer, Labrador retriever, English setter, Great dane, Poodle, and Siberian husky (Smith, 2003). German shepherd dog has been reported to has an increased risk with an odds ratio of 4.7, compared to other purebred dogs (Prymac et al., 1985). More recently hemangiosarcoma appears to has become a signifi cant problem in Golden retrievers in North America with an estimated life-time risk of 1 in 5 reported by the Golden Retriever Club of America (Tamburini et al., 2009;Dobson, 2013). Th e tumour occurs predominantly in older dogs between 8 and 10 years of age; mean age at time of diagnosis is 9 to 12 years (Sharma, 2012). Labrador retriever and Golden retriever dog breeds count for a high ratio of visceral hemangiosarcomas and skin hemangiomas and a slightly lower ratio of nonvisceral hemangiosarcoma. Dogs with hemangiomas are younger than those with hemangiosarcoma. Any type of hemangiosarcoma is rare in young dogs (Schultheiss, 2004).
Th e epidemiological study performed by Mialot and Lagadic (1990) remarked positive correlation between age of dogs and cats with tumour incidence. Th e increase in tumour incidence is correlated until the age of 10 years with animal age, in both dogs and cats. Tumour frequency remains high until the age of 12 years in dogs and 13 years in cats, then it gradually reduce, because of the life duration of these species.
Th ere is no evidence which support addiction of dogs trained to detect hard narcotics, or even run the risk of becoming addicted, to the narcotics which they are trained to detect. A sniff er dog during the training for narcotic detection does not come in physical contact with narcotic agents. Th e only contact the dog has with the narcotic sample is related to sniffi ng the sample package. Two cases of malignant tumour in dogs that are used for the detection of narcotics are insuffi cient to examine the relationship between tumour occurrences in these working dogs. In the literature there is no enough information about what kind of impact drugs can have on the health of sniff er dogs and the occurrence of tumours in this breed, although many drug-induced diseases are known in human population (Irey, 1976;Challita et al., 2014). It has been confi rmed that neoplastic changes were the second leading cause of death or euthanasia in working dogs in the USA (Moore et al., 2001). Th is fi ndings may suggest a possible role of chronic drug exposing to occurrence of neoplastic changes in sniffi ng dogs, so the further investigations may determinate the possible correlation.