Thursday, March 24, 2011

Dysphagia

DEFINITION
Difficulty swallowing, resulting from the inability to prehend, form, and move a bolus of food through the oropharynx into the esophagus
Esophageal dysphagia is discussed under the topics Megaesophagus and Regurgitation.

PATHOPHYSIOLOGY
Swallowing difficulties can be caused by mechanical obstruction of the oral cavity or pharynx, neuromuscular dysfunction resulting in weak or uncoordinated swallowing movements, or pain associated with prehension, mastication, or swallowing.
Oral dysphagia refers to difficulty with the voluntary components of swallowing—prehending and forming a bolus of food at the base of the tongue
Pharyngeal dysphagia occurs when there is a malfunction of the involuntary movement of the food bolus through the oropharynx.
Cricopharyngeal dysphagia refers to abnormal movement of the food bolus from the pharynx through the cricopharyngeus muscle, caused by either failure of the cricopharyngeus to relax (cricopharyngeal achalasia) or asynchrony between pharyngeal contractions and cricopharyngeus opening (cricopharyngeal asynchrony).
Deglutition is coordinated by the swallowing center in the brainstem; sensory afferents are transmitted to the swallowing center by CNs V and IX.
Motor efferents responsible for swallowing are carried by CN V, VII, XII (prehension and mastication) and IX and X (pharyngeal contraction); disorders in any of these areas may result in dysphagia.

Distemper - Dogs

DEFINITION
An acute to subacute contagious febrile and often fatal disease with respiratory, gastrointestinal, and CNS manifestations
Caused by CDV, a morbillivirus in the Paramyxoviridae family
Affects many different species of the order Carnivora; mortality rate varies greatly among species.

PATHOPHYSIOLOGY
Natural route of infection—airborne and droplet exposure; from the nasal cavity, pharynx, and lungs, macrophages carry the virus to local lymph nodes, where virus replication occurs; within 1 week, virtually all lymphatic tissues become infected; spreads via viremia to the surface epithelium of respiratory, gastrointestinal, and urogenital tracts and to the CNS
Fever for 1–2 days and lymphopenia may be the only findings during initial period; further development depends on the virus strain and the immune response.
Strong cellular and humoral immune response—may remain subclinical
Weak immune response—subacute infection; may survive longer
Failure of immune response—acute death within 2–4 weeks after infection; convulsions and other CNS disturbances frequent causes of death

Capillariasis

Capillaria plica is a parasite that invades the mucosa or submucosa of the bladder or (rarely) the renal pelvis and ureter, causing a mild inflammatory response.
C. plica in dogs and cats and C. feliscati in cats have been uncommonly associated with signs of lower urinary tract disease.
First stage in life cycle of C. plica is passage of bipolar ova in urine. After earthworms ingest embryonated ova, the parasite develops into the infective stage. Ingestion of infective earthworm results in a patent infection in dogs in 58–88 days.
Details of life cycle of C. feliscati are poorly understood.

Babesiosis

RBC destruction and anemia caused by Babesia spp. of intracellular protozoa
B. cani—a large (4–7 mm-long), pear-shaped parasite of canine RBCs; in the U.S., strains generally cause mild or inapparent disease in adults (unless immunosuppressed), but severe disease in pups; South African strains cause severe disease and death in some adult dogs.
B. gibsoni—a small (2.5 mm), ring-shaped organism that causes severe disease in most infected adult dogs; rare in the U.S. but common in Africa and Asia; organisms can be difficult to see in stained blood films.
B. felis—a very small (1 mm), ring-shaped organism that occurs in cats in Africa and southern Asia; of similar size and morphology to Cytauxzoon felis, which occurs in cats in the U.S.

Alopecia

DEFINITION

Common disorder
Characterized by a complete or partial lack of hair in areas where it is normally present
May be associated with a multifactorial cause
May be the primary problem or only a secondary phenomenon

Actinomycosis

OVERVIEW
An infectious disease caused by gram-positive, branching, pleomorphic, rod-shaped bacteria of the genus Actinomyces
A. viscosus—most commonly identified; survives in microaerophilic or anaerobic conditions
Rarely found as the single bacterial agent in a lesion; more commonly, it is a component of a polymicrobial infection.
There may be synergism between Actinomyces and other organisms.

SIGNALMENT
Dogs and cats
Especially common in young male dogs of sporting breeds

SIGNS
Infections—usually localized; may be disseminated; cervicofacial area commonly involved
Cutaneous swellings or abscesses with draining tracts—yellow granules (“sulfur granules”) may be seen in associated exudates.
Pain and fever
Exudative pleural or peritoneal effusions
Retroperitonitis—in one study, Actinomyces was identified in 3 of 34 affected dogs
Osteomyelitis of vertebrae or long bones—probably secondary to extension of cutaneous infection; lameness or a swollen extremity may develop
Motor and sensory deficits—reported with spinal cord compression by granulomas