Occurrence of canine lymphoproliferative disorders in and around Namakkal, Tamil Nadu

Introduction

Lymphatic system is the most vital system in the body, which plays a crucial role in both removal and spread of diseases from one area of the body to another (Mohanty and Wilkinson, 2013) [10] . LNs are the first organ that reacts to inflammation or immune response in the disease conditions. LN enlargement is a common finding in dogs and it is a clinical symptom rather than a definite disease which indicates a number of underlying factors. The common causes of LN enlargements are oedema, reactive hyperplasia, inflammation, infection and neoplasia (Cowell et al. 2003; Sapierzynski and Micun, 2009) [2,12] . LPD is characterized by the enlargement of the LNs as solitary, regional or generalized. It is a heterogenous group of malignant clonal proliferations of lymphocytes. LPD occurs due to impaired immunity caused by immunodeficiency or immunodysregulatory syndromes and usually occurs secondary to bacterial/viral/fungal infections. This paper elucidates the influence of intrinsic factors on the occurrence of LPDs in dogs.

Materials and Methods

A total of 14,765 dogs were brought to the Veterinary Clinical Complex, Veterinary College and Research Institute, Namakkal from November 2022 to October 2023. Among these dogs, 7,246 cases were presented to the Veterinary Clinical Medicine unit for treatment. Out of these canine patients, 66 dogs were diagnosed with LPDs. The animal details like breed, age and sex were recorded from LPD affected dogs. The clinical signs in LPD affected dogs varied with primary conditions like skin infections or mite infestations, haemoprotozoan diseases, pyogranulomatous lymphadenitis and lymphoma. The enlargement of LNs is the consistent finding among all the LPD affected dogs.

Results and Discussion Incidence

The annual incidence rate of LPD in dogs recorded as 0.91% (66/7246) in this study is more than the earlier observations made by Teske (1994) [13] , Atherton and Mason (2022) [1] and Zandvliet (2016) [15] . Teske (1994) [13] reported the annual incidence of canine non-Hodgkin lymphoma is 13 to 24 out of 1,00,000 dogs. Jagielski et al. (2002) [4] diagnosed 83% of lymphomas from haematopoietic cancers with high incidence among all tumors in dogs. Kojima et al. (2021) [7] observed the most prevalent extranodal lymphoma is gastrointestinal lymphoma which accounts for 5 to 7% of all lymphomas in dogs. Majority of the intestinal lymphomas are from T-cell origin in dogs. More prevalent B-cell lymphomas in humans are diffuse large B-cell lymphoma (DLBCL) and mucosa associated lymphoid tissue (MALT) lymphoma. Atherton and Mason (2022) [1] stated that the most prevalent haematologic malignancies in canines is lymphoma with annual incidence rate of 25 per 1,00,000 dogs.

Breed

The occurrence of LPDs in various breeds of dogs is presented in Graph 1. Among the breeds, mongrels (n=18) are affected more followed by pure breeds. The breed wise incidence recorded in this study is similar to the findings of Sapierzynski and Micun (2009) [12] , Villamil et al. (2009) [14] and Jark et al. (2020) [5] . These observations are contradicted to the findings of Mylonakis et al. (2011) [11] who stated pure breeds are predisposed more than mongrels. Villamil et al. (2009) [14] recorded the most common breeds affected with LPDs are Golden retriever, Labrador retriever, German shepherd, Boxer and mixed breeds mainly due to heritable factors. The breeds that are dominant in the population determined the incidence due to environmental and genetic factors.

Graph 1: Breed wise incidence of lymphoproliferative disorders in dogs

Age

The occurrence of LPD in different age group of dogs is presented in Graph 2. The mean age of the dogs affected with LPD is 4.32 years and it ranged from 2 months to 13.5 years.

The highest incidence was recorded in the age between 1 and 3 years. The age of the dogs affected with LPDs in this study is in agreement with Jark et al. (2020) [5] who observed 15.8% of the dogs with less than 5 years of age are affected with LPDs. These observations are different from the findings of Teske (1994) [13] , Sapierzynski and Micun (2009) [12] and Atherton and Mason (2022) [1] who recorded the mean age of the dogs affected with LPDs are more than 6.3 years. Teske (1994) [13] observed the mean age of the dogs affected with canine non-Hodgkin lymphoma is ranged from 6.3 to 7.7 years. Zandvliet (2016) [15] recorded the occurrence of lymphoid neoplasia at all age groups but predominantly noticed in the middle aged to older dogs with the incidence of 1.5 cases per 1,00,000 dogs is < 1 year of age to 84 cases per 1,00,000 dogs is > 10 years of age.

Graph 2: Age wise incidence of lymphoproliferative disorders in dogs

Sex

The LPDs observed more in males (n=47) than females (n=19) of this study is agreed to the observations of Jagielski et al. (2002) [4] , Villamil et al. (2009) [14] and Mylonakis et al.

(2011) [11] and contrary to Jark et al. (2020) [5] . Villamil et al.

(2009) [14] recorded that the male dogs have more sex predisposition to lymphoma than females at and above 4 years of age. Zandvliet (2016) [15] recorded the occurrence of lymphoid neoplasia at all age groups without sex predisposition. The intact females have reduced risk in contrast early sterilization showed increased risk.

Clinical signs

The dogs with skin infections or mite infestations exhibited localized or generalized LN enlargement depending on local or diffuse skin affections. The haemoprotozoan diseases affected dogs revealed multiple LN enlargements, ecchymotic patches in the ventral abdomen and splenomegaly. The dogs affected with pyogranulomatous lymphadenitis revealed abscessation of entire LN containing purulent material and fever. The dogs affected with lymphoma exhibited multiple LN enlargements, splenomegaly, limb edema, corneal opacities, ascites and respiratory distress. The clinical signs exhibited by the dogs affected with LPD of this study are similar to the observations of Kol et al. (2013) [8] , Jung and Jung (2014) [6] and Long et al. (2020) [9] . Ghernati et al. (2000) [3] reported that the dog with chronic large granular lymphocytic leukemia exhibited diarrhoea and moderate polydipsia. The physical examination of the dog showed moderate splenomegaly without hepatomegaly or LN enlargement. Kol et al. (2013) [8] observed in dogs affected with LPDs exhibited moderately enlarged right mandibular LN of 1.5 cm in diameter and noticeably swollen right inguinal LN of 3.5 cm in diameter. Palpation of abdomen revealed hepatomegaly and abdominal mass. Jung and Jung (2014) [6] reported that the dogs with leukemia revealed abdominal distension, dyspnoea, lethargy, anorexia and weight loss. Physical examination of the dog revealed splenomegaly. Long et al. (2020) [9] observed an acute, non-painful facial swelling of right mandibular region which revealed marked lymphadenopathy of submandibular LN on palpation in dogs affected with lymphoid tumors.

Conclusion

The occurrence of LPDs in dogs was influenced by many intrinsic factors. The LPDs affected dogs showed clinical signs based on the primary conditions like skin infections or mite infestations, haemoprotozoan diseases, pyogranulomatous lymphadenitis and lymphoma. Very few reports are available on the occurrence of LPDs influenced by these factors; hence, the report is presented.

Acknowledgement

AcknowledgementsThe authors are thankful to the Tamil Nadu Veterinary and Animal Sciences University for providing facility to carry out the research work.

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