List of five major neoplastic diseases found in birds:- 1. Virus-Induced Neoplastic Diseases Marek’s Disease 2. Lymphoid Leukosis 3. Myelocytomatosis 4. Erythroblastosis 5. Adenocarcinomatosis.
Neoplastic Disease # 1. Virus-Induced Neoplastic Diseases Marek’s Disease (MD):
(i) Acute (visceral) form:
It is characterized by diffuse or nodular lymphomatous lesions in various viscera (liver, spleen, heart, kidneys, lungs, gonads, proventriculus, pancreas, etc.), the skeletal muscles and the skin. MD affects mainly hens, and is rarely observed in turkeys.
It is most commonly encountered in birds at the age of 89 weeks and in layer hens. The cases at the age of 16- 20 and 24-30 weeks are predominant. MD is prevalent all around the world and, in fact, all flocks are exposed to the effect of the aetiological factor. Diffuse lymphomatous growths in the heart result in its transformation into an amorphous tumorous mass.
ADVERTISEMENTS:
Lymphoid cell proliferations occur in the iris and the ciliary muscles in the ocular form of MD. Three classes of viruses are able to protect fowl from MD: attenuated serotype 1 of MDV-cell associated vaccines; HVT could be used for preparation of cell- free lyophilized vaccines; naturally apathogenic isolates of serotype 2 cell associated vaccines.
The vaccines against MD provide over 90% protection. HVT gives excellent results but in case of failure, a bivalent vaccine could be used.
(ii) Transient paralysis:
They are observed in chickens and hens, especially non-vaccinated against MD. Most cases present the classical form manifested by flaccid paralysis of the neck and legs for 143 days followed by complete recovery. The syndrome has to be differentiated from the neural form of MD on the basis of its transient nature and the flaccid, but not spastic paralysis.
Neoplastic Disease # 2. Lymphoid Leukosis:
ADVERTISEMENTS:
It is characterized by a gradual beginning, persistent low mortality in the flock and diffuse or focal neoplastic growths of lymphoblasts in viscera. The neoplastic changes begin always from the bursa of Fabricius, where various-sized lymphomas are detected.
Clinically, pale comb and wattles, sometimes swelling of the abdomen because of the highly enlarged liver are observed. Diffuse or nodular neoplastic growths could be detected in many organs, but they are more common in liver, spleen, kidneys, heart and ovary.
Usually, it is not seen in birds younger than 14 weeks. The lethal tissues occur mostly at the age between 24 and 40 weeks. Distinct nodular tumours. Tumours in the bursa of Fabricius.
Neoplastic Disease # 3. Myelocytomatosis (MC):
MC is caused by viral strains of ALSVs from subgroups A, B and J (MC29, MC31, CMII, OK 10, HRPS 103, and ADOL HC1). It is encountered relatively infrequently. Its occurrence is sporadic or enzootic. Susceptible birds are hens, pheasants, guinea hens and quails. In most cases, the liver is enlarged, thick and mottled with dark red spots or fat-like nodules.
ADVERTISEMENTS:
Sclerotic changes in the liver are possible because of regression of neoplastic lesions. The spleen is usually enlarged, but sometimes, could be atrophied. Carcinosarcoma of the pancreas. Tubulous glandular epithelial formations of the carcinoma component among the lipo- sarcoma part of the parenchyma.
The diagnosis is based upon the entity of data about the history, the gross appearance and location of the tumours and the specific histological lesions. From a differential diagnostic point of view, myeloblastosis and erythroblastosis should be considered.
Neoplastic Disease # 4. Erythroblastosis:
Erythroblastosis (ER) is characterized by intravascular proliferations of immature precursors of erythrocytes. ER has a leukaemic character and is manifested with signs of severe anaemia. The liver and the kidneys are moderately enlarged with a characteristic dark red to mahogany colour, sometimes with haemorrhages.
ER is caused by the avian eryhtroblastosis virus (AEV); the most frequently encountered strains are E-26, ES4, R, etc. The spleen is unusually enlarged or atrophied in cases of severe anaemia. Osteopetrosis is a neoplastic disease. It is characterized by a significant thickening of bone periosteum. The diaphyses of the tibia and/or tarsometatarsal bones are most commonly affected.
Neoplastic Disease # 5. Adenocarcinomatosis:
The intestinal and reproductive tracts are primarily affected. Quite often, the neoplasms invade the peritoneum and other serous coats. Macroscopically they appear as numerous disseminated thick nodes of various sizes (with a diameter from several mm to 1 cm).
Sometimes, the tumours are of cystic formations (cystadeno-carcinoma). The leiomyoma of the mesosalpinx is a common tumour in hens. Usually, it is located in the ventral ligament of the oviduct. Its size varies from small to large (several cm in diameter), smooth, thick, sometimes highly vascularized nodes.