Veterinary Pathology is an important discipline of Veterinary Sciences which makes a bridge in between the basic and clinical sciences. The knowledge of Veterinary Pathology makes the Veterinarian a perfect diagnostician particularly when his patients (animal) can’t speak their illness to the doctor. Keeping in view the need of study of Veterinary Pathology to become a good Veterinary doctor, the book “Systemic Veterinary Pathology” is written for the use of teachers, students and field veterinarians. The complexity of the subject is presented in a simplified way particularly keeping the view of Indian geo-climatic conditions and animal population. However, students of Veterinary Science desire a compact text of Systemic Veterinary Pathology covering the VCI new syllabus of Pathology which can be utilized during their study and examinations particularly in competitive examinations. Hence, this textbook is prepared as a text material to all those who want to study Systemic Veterinary Pathology at undergraduate and postgraduate level and are interested in any kind of competitive examination or interview. It covers all the topics of Systemic Veterinary Pathology like Pathology of cutaneous system, musculoskeletal system, cardiovascular system, respiratory system, digestive system, hemopoietic and immune system, urinary system, genital system, nervous system, endocrine system, eyes and ear. The text is described in a very simple format including developmental as well as acquired pathological conditions in different body systems of animals and birds including their etiology, clinical manifestations, characteristic macroscopic and microscopic features along with diagnosis; only salient features are mentioned avoiding detailed text. Hope this book “Systemic Veterinary Pathology” not only will f ind a place in the young fraternity of Veterinary Science but also it will be highly useful to the field Veterinarians for diagnosing diseases on the basis of characteristic clinical manifestations, and lesions and in writing of post mortem report. The help rendered by our colleagues and students in preparation and designing of this book is duly acknowledged. Readers’ comments are welcome to further improve the book.

Developmental Anomalies Congenital icthyosis Congenital icthyosis is scaly epidermis which resembles the skin of fish and occurs due to a simple autosomal recessive homozygous gene in calves. This condition is characterized by scaly, horny, thick epidermis divided into plates by deep fissures. Microscopically, there is thick keratin layer over the epidermis (Fig.1.1). Epitheliogenesis imperfecta Epitheliogenesis imperfecta is a congenital defect characterized by discontinuity of epithelium on skin leaving patches without squamous epithelium mostly at feet, claws and oral mucosa. Such defect may occur in calves which succumb to infection after birth or such foetus may abort. This disease condition is inherited as an autosomal recessive trait.

Pathology of Muscles Equine Rhabdomyolysis It is also known as Azoturia or Monday Morning Disease. The disease occurs in well fed horse after a spell of inactivity. Suddenly after walking a few steps, the horse is unable to move further and feels pain with intense sweating and hardening of muscles. Etiology • Accumulation of lactic acid in muscles. • High glycogen storage. • Lack of oxygen supply. Macroscopic features • Hardening of muscle just like wood. • Urine is dark brown with myoglobin – myoglobinuria. • Tonic spasms in muscles. • Atrophy of affected muscles in chronic cases.

Developmental Anomalies Persistent right aortic arch This is a developmental anomaly of aorta in which the aorta develops from right arch present on right side of trachea and oesophagus. The ductus arteriosus forms a ring around trachea and oesophagus by connecting aorta and pulmonary artery. This ring causes partial obstruction of trachea and/or oesophagus. Patent ductus arteriosus The ductus arteriosus is a short blood vessel which connects pulmonary artery to aorta in foetal life for diversion of blood. Normally, soon after birth this duct is sealed and remains in the form of a ligamentum arteriosum. But sometimes this ductus arteriosus remains open and blood is continuously shunted between aorta and pulmonary artery, after leading to congestive heart failure, pulmonary hypertension and cyanosis due to mixing of venous and arterial blood (Fig. 3.1).

Pathology of Upper Respiratory Tract In many infectious diseases, there is inflammation of mucosa of upper respiratory passage leading to nasal discharge which is catarrhal, purulent or fibrinous, depending on the type of infection. The infection may extend to lower parts of respiratory tract and reach the lungs causing pathological alterations. Rhinitis is the inflammation of nasal mucosa (Fig. 4.1). Sinusitis is the inflammation of sinuses e.g. frontal sinusitis in dehorned cattle. The larvae of botfly Oestrus ovis enter the nasal passage and migrate up to frontal sinuses and turbinate bones and cause mucopurulent inflammation. Similarly, leeches (Dinobdella ferox) is known to cause nasal cavity inflammation in domestic animals and suck blood. Rhinitis is caused by Bordetella bronchiseptica in pigs and is characterized by mucopurulent exudate, disappearance of nasal septum, retarded growth of snout and plugging of passage by solidified exudate and dead tissue. This condition is known as porcine atrophic rhinitis. Epistaxis is bleeding from nasal passage due to trauma, neoplasm (Fig.4.2A) and ulcerative lesions as a result of infections (Fig.4.2B). Pharyngitis is the inflammation of pharynx while laryngitis is the inflammation of larynx.

Developmental Anomalies Epitheliogenesis imperfecta of tongue Abnormal smooth surface of tongue due to small filiform papillae. It occurs as a defect in autosomal recessive gene and occurs in Holstein-Friesian cattle. This is also known as smooth tongue. Cleft palate This is most common congenital abnormality that occurs due to failure of oral nasal cavity to divide leaving cleft. It may also extend towards lips producing ‘harelip’ condition. Mega colon There is distention of colon which abruptly terminates in rectum due to mutant gene in dogs.

Developmental Anomalies Hereditary anemia Hereditary anemia has been reported in mice due to defects in erythropoiesis or reduced vitality of erythrocytes. Erythropenia along with leucopenia occurs in mouse foetus on 20th day of gestation due to defective autosomal chromosome 4. Sex linked anemia in mouse is hypochromic with deficient bone marrow and occurs in hemizygus males or homozygus females. This anemia occurs due to deficiency of iron as a result of poor absorption from gastrointestinal tract. Autoimmune hemolytic anemia in foals It occurs due to incompatible blood group antigens of male and female parents. The mare does not have that blood group antigen but foetus acquires it from father. The foetal blood exposed to dam through placental exchanges leads to induction of antibody production in mares against foetal blood group antigen. These antibodies accumulate in colustrum and when foal suck the milk from mares, they are readily absorbed through G.I. tract of foals in blood and cause destruction of erythrocytes leading to anemia.

Developmental Anomalies Aplasia Absence of one or both kidneys. Absence of one kidney is observed in animals with compensatory hypertrophy of another kidney and such animals may survive well. Hypoplasia The size of kidneys remains small as they don’t grow properly due to defect in a single recessive autosomal gene. Cyst in kidney Single or multiple cysts in pig and dog kidney are reported with tinged yellow colour. They may arise from nephron due to its distension. Presence of multiple cysts is also termed as congenital polycystic kidney. Type-I cysts are formed due to dilation and hyperplasia of collecting tubules resulting in spongiform kidneys. In such neonates cystic bile ducts are also present.

Female Genital System Developmental Anomalies Agenesis Absence of ovary, uterus, oviduct and cervix in females. It may be unilateral or bilateral. Hypoplasia Complete or partial lack of germ cells in ovaries. Hypoplasia of uterus is related with agenesis of gonads. Ovaries of freemartin are also hypoplastic. Hermaphrodite animal has ovary and testicular tissue both in the gonads. Hermaphroditism In hermaphrodites, there is presence of organs of both sexes in same individual animal. Both ovarian and testicular tissue occur in one animal leads to sterility in animal (true hermaphrodite) while in pseudohermaphrodite the gonadal tissue of only one sex is present but there is some degree of development of opposite sex organs.

Nervous system is composed of brain, spinal cord, and peripheral nerves. The neuron is a basic functional unit of nervous system. Necrosis of neurons in brain is known as encephalomalacia while necrosis of neurons in spinal cord is termed as myelomalacia. If the necrosis occurs in grey matter it is known as polioencephalomalacia while necrosis of neurons in white matter is called as leukoencephalomalacia. There are three types of scavenger cells in nervous system known as microglial, oligodendroglial and astrocytes. Microglial cells surround the necrotic neurons and are known as satellite cells and the process is called as satellitosis. As the neuron dies, it is engulfed by microglial cell and this process is termed as neuronophagia. The necrosis of nerve fibers starts from myelin sheath and this change is called demyelination or Wallerian degeneration.

Nervous system is composed of brain, spinal cord, and peripheral nerves. The neuron is a basic functional unit of nervous system. Necrosis of neurons in brain is known as encephalomalacia while necrosis of neurons in spinal cord is termed as myelomalacia. If the necrosis occurs in grey matter it is known as polioencephalomalacia while necrosis of neurons in white matter is called as leukoencephalomalacia. There are three types of scavenger cells in nervous system known as microglial, oligodendroglial and astrocytes. Microglial cells surround the necrotic neurons and are known as satellite cells and the process is called as satellitosis. As the neuron dies, it is engulfed by microglial cell and this process is termed as neuronophagia. The necrosis of nerve fibers starts from myelin sheath and this change is called demyelination or Wallerian degeneration.

Pathology of Endocrine System Pathology of Hypothalamus The lesions in hypothalamus may cause diabetes insipidus characterized by polydipsia and polyuria with low specific gravity of urine. It occurs due to deficiency of antidiuretic hormone vasopressin. Etiology/ Occurrence • Lesions in hypothalamus and/or pituitary. • Adenoma and adenocarcinoma of pituitary. • Necrosis of hypothalamic nuclei due to larval migration.

A Abortion 172, 173, 174 Abscess 15, 27, 29, 88, 93, 147, 154, 166, 182, 183, 188, 191 Abscessation 94 Abscess formation 29, 93, 154, 155, 166 Absolute eosinophil 135 Acanthosis nigricans 2 Acariasis 6 Accumulation of blood 40, 41, 64 Acini 198 Actinomyces bovis 180, 204, 205 Actinomyces pyogenes 27, 43, 154, 167, 168, 176, 177, 182, 184 Actinomycosis 27, 81, 205