Congenital and Neonatal Disease - Pathology

()Map GENERAL PATHOLOGY (Map)

Introduction

• Changes in the patterns of growth and differentation result in growth disorders.
  • These changes may be in single cells, tissues or organs.
• There are two types of growth disorders.
  1. Malformations
     • Occur during gestation.
  2. Congenital
     • Detected at birth.
• Some growth disorders have a heriditary input.
  • Occur as a result of genetically transmitted disease.
• Some growth disorders occur as a sequl to a variety of insults to the foetus during gestation.
• Only a few malformations are readily accessible to surgical correction.

Causes of Malformations

• There are many causes of malformations in animals.
• If the insult occurs early in gestation and is sufficiently severe, it will result in foetal death, resorption and infertility.
• If the insult occurs late in gestation, the malformation will be more limited and the foetus usually survives.

Chromosomal Defects

• Although malformations can be caused by chromosomal abnormalitis, these often result in early abortion or resorption.

Viral Diseases

• Some viruses are able to cross the placenta and cause damage to foetal tissues.
• For example:
  • Border Disease Virus in lambs.
  • Cerebellar hypoplasia in kittens caused by parvovirus.

Toxins

• For example, toxic plants ingested by the dam during pregnancy.
  • Veratrum californicum
    • May produce cyclopia in lambs when ingested by the dam in early pregnancy.

Drugs

• Griseofulvin
  • Used to treat "ringworm" (dermatophytosis). ( for the treatment of dermatophytosis - 'ringworm' )
  • Can cause serious malformations in kittens if administered to a pregnant queen.
• Oestrogens and Actinomycin D have also been associated with malformations.

Ionising Radiation

• For example, X-rays.

Nutritional Deficiencies

Copper Deficiency

• Copper deficiency in the pregnant ewe can result in "swayback'" in lambs.
  • Due to white matter degeneration in the central nervous system of prenatal and neonatal lambs.
• The degeneration is thought to be a mixture of both hypomyelination and demyelination.
• The central nervous system of the lambs is affected.
  • Neonatal lambs show an ataxia in the first few weeks of life.
    • Due to demyelination of dorsolateral and ventromedial tracts in the white matter of the spinal cord.
  • More severe lesions can be present in lambs affected prenatally.
    • Destruction of subcortical white matter in the brain.
      • The extent of this varies.
• It is unknown how copper deficiency exerts this effect.
  • Supplementation in pregnancy prevents the prenatal form.
  • Supplementation in the first few weeks will alleviate the neonatal form.

Vitamin Deficiencies

• Vit. A and D deficiency can result in skeletal malformations.

Physical Factors

• For example, adhesions between foetal membranes or umbilical cord.
  • Can result in amputation of skeletal segments.
    • Especially around limbs.

Anoxia

• Lack of oxygen in gestation can result in malformations.

Malformations

Cyclops

• The presence of a single central eye as a result of facial deformity.

Bulldog Calf

• A well recognised deformation in Dexter calves.
• Related to defective cartilage matrix and abnormal ossification.
• The calf is born with short and crooked limbs and the facial bones are short.

Cleft Palate

• A very common malformation in many species.
• Due to failure of the palatine bones to fuse in the midline.
• The animal:
  • Fails to suckle properly
  • Can develop an aspiration pneumonia.
• Caused by:
  • Administration of griseofulvin to queens during pregnancy.
  • Certain viral infections.
  • Ingestion of toxic plants.

Cystic Kidney

• Also known as polycystic kidney.
• Can be seen in many different species.
• Can have a hereditary basis.
• The cysts may be single or multiple.
• Results from the failure of development of the tubular system in nephrons.
• Severely affected animals may die of renal failure early in life.
  • The affected kidney does not have enough functional reserve, and so small infections can have a serious effect on renal function.

Spina Bifida

• A failure of closure of the vertebral arch.
• May result in herniation of the meninges and /or spinal cord.
  • There may be a direct communication between those structures and the skin surface.

Hydrocephalus

• Not uncommon in dogsand cats.
• Abnormal drainage of cerebrospinal fluid (CSF) results in dilation of the ventricles of the brain.
  • Is a result of either stenosis of:
    • The aqueduct between the 3rd and 4th ventricle, or
    • The foramina further back in the brain stem.
  • May also be acquired as a result of compression by tumours or infectious processes.
• Dilation of the ventricles with CSF causes pressure atrophy of the overlying brain tissue.
• Hydrocephalus can be seen at birth.
  • Characterised by a dome shaped skull and open fontanelles.
• Hydrocephalus may also be hidden and detected later in life.

Cerebellar Hypoplasia

• The cerebellum is smaller than normal and oftenrudimentary.
• Microscopy shows a highly disorganised architecture.
• The animal shows tremors and ataxia.
• Usually associated with viral infections during gestation.

Skeletal Malformations

• There are numerous skeletal malformations.
• Include:
  • Absence of bones
  • Deformation
  • Shortening
  • Duplication
  • Hypoplasia

Skin Defects

• E.g. Epitheliogenesis imperfecta.
  • There is absence of portions of the epidermis.
    • Results in ulcers.

Muscular Defects

• E.g. defects in the thoracoabdominal walls resulting in exterioration of internal viscera.
  • Called "shistosoma".

Cardiac Defects

• There are several possible types of cardiac defects.
  • These include:
    • Patency between chambers
    • Persistent right aortic arch
    • Tetrology of Fallot.

Sexual Organ Malformation

• E.g.:
  • Hermaphrodites
  • Pseudohermaphrodites
  • Freemartinism in females calves.

Metabolic Diseases

• "Storage" diseases.
  • Vital enzymes are missing or defective within all cells.
• These diseases express themselves as storage of intermediate products within cells.
• Because neural tissue is a very sensitive tissue and cannot repair, these diseases usually express themselves as disease of the Central Nervous System.