VIRAL DISEASES

RABIES (Hydrophobia)

An acute infectious disease of mammals, especially carnivores, characterized by CNS pathology leading to paralysis and death.

Etiology and Epidemiology

Rabies is caused by a neurotropic virus often present in the saliva of rabid animals

Pathology

The virus travels from the site of entry via peripheral nerves to the spinal cord and the brain, where it multiplies; it continues through efferent nerves to the salivary glands and into the saliva.

microscopic examination shows perivascular collections of lymphocytes but little destruction of nerve cells. Intracytoplasmic inclusion bodies (Negri bodies), usually in the cornu Ammonis, are pathognomonic of rabies, but these bodies are not always found.

Sign/Symptoms

In humans, the incubation period varies from 10 days to > 1 yr and averages 30 to 50 days.

Rabies commonly begins with a short period of depression, restlessness, malaise, and fever. Restlessness increases to uncontrollable excitement, with excessive salivation and excruciatingly painful spasms of the laryngeal and pharyngeal muscles. The spasms, which result from reflex irritability of the deglutition and respiration centers, are easily precipitated Hysteria due to fright

Prognosis and Treatment

Death from asphyxia, exhaustion, or general paralysis usually occurs within 3 to 10 days after onset of symptoms

Eosinophilia:
Causes

-Allergic disorders.
-Parasitic infection.
-Skin diseases.
-Pulmonary eosinophilia.
-Myeloproliferative lesions and Hodgkin's disease.

Immunodeficiency

This may be :-

• Congenital (Primary)
• Acquired (Secondary)

Features : Complete or near complete lack of T & B lymphoid tissue. Fatal early in life Even with marrow grafting, chances of graft versus host reaction is high.

B. T Cell Defects :

• Thymic dysplasia
• Digeorge’s syndrome
• Nazelof’s syndrome
• Ataxia teltngiectaisa
• Wiscott Aldrich’s syndrome

These  lessons show predominantly defective cell mediated immunity. But they may also show partial immunoglobulin defects cell mediated immunity. But they may also show partial immunoglobulin defects due to absence og T-B co-operation.

C. Humoral immunity defects.

Bruron type- aggammaglobulinaemia.

• Dysgammaglobulinaemias-variable immunodeficiency’s of one or more classes.

Acquired deficiency

A. Immuno suppression by :

• Irradiation.
• Corticoids.
• Anti metabolites.
• Anti lymphocyte serum.

B. Neaplasia  of lymphoid system :

• Hodgkin's and Non Hodgkin's lymphomas.
• Chronic lymphocytic leukaemia..
• Multime myeloma and other paraproteinaemias (normal immunoglobulins reduced in spite of hyperglobulinaemia).

c. excessive protein loss.

• Nephrotic Syndrome.
• Protein losing enteropathy.

INFLUENZA

An acute viral respiratory infection with influenza, a virus causing fever, coryza, cough, headache, malaise, and inflamed respiratory mucous membranes.

Influenza B viruses typically cause mild respiratory disease

Symptoms and Signs

mild cases:

Chills and fever up to 39 to 39.5° C

Prostration and generalized aches and pains, Headache, photophobia and retrobulbar aching

Respiratory tract symptoms may be mild at first, with scratchy sore throat, substernal burning, nonproductive cough, and sometimes coryza. Later, the lower respiratory illness becomes dominant; cough can be persistent and productive.

severe cases

sputum may be bloody. Skin is warm and flushed. Soft palate, posterior hard palate, tonsillar pillars, and posterior pharyngeal wall may be reddened, but no exudate appears. Eyes water easily, and the conjunctiva may be mildly inflamed

Encephalitis, myocarditis, and myoglobinuria are infrequent complications of influenza and, if present, usually occur during convalescence

Viral meningitis
1. Can be caused by many different viruses, including cytomegalovirus, herpes virus, rabies, and HIV.
2. CSF fluid from a spinal tap differs from that seen in a bacterial infection. It shows mononuclear cells, higher levels of protein, and normal levels of glucose.

DYSPLASIA
 It is disturbed growth or  cells in regard to their size, shape arrangement. In its mild degrees it represents a reversible reaction to chronic inflammation whereas the most severe degrees warrant a labelling of intraepithelial neoplasia. Hence it includes a wide spectrum of changes ranging from a reversible disorientation to 'carcinoma-in-situ'.

Histologically it is characterized by:

o    Basal cell hyperplasia.
o    Variation in size and shape of cells.
o    Disorderly maturation.
o    Increased mitotic activity.
o    Disorientation of arrangement of cells (loss of polarity)

Dysplasia is commonly seen in:

o    Squamous epithelium of cervix.
o    Bronchial epithelium in habitual smokers.
o    Gastric and colonic mucosa in long standing inflammation
o    Oral and vulval leucoplakia