General terms for disease
General terms for disease are latent period (incubation period), prodromal period, period of manifestation, outcome of the disease, recovery, relapse, complications, convalescence, sequele, and death.
Latent period
Latent period is also termed as incubation period in infectious disease. It is the period from entry of the agent into the animal till the manifestation of detectable clinical signs. Latent period ranges from several minutes to several months.
Examples of latent periods are:
- Ruminal lactic acidosis: 6 to 12 hours
- In most infectious diseases: 7 to 10 days
- In diseases like BSE (bovine spongiform encephalopathy): 6 to 8 years
Prodromal period
Prodromal period lasts from discovery of first sign of the disease to its complete manifestation.
On set of infectious diseases are invariably characterized by indefinite manifestation such as general depression, chills, inappetence, rise of temperature etc.
Period of manifestation
Period of manifestation of disease usually follows the prodromal period. It is the period of development of marked clinical manifestations. These help the clinician to diagnose the disease through the very characteristic features of the particular disease.
Examples of Period of manifestation are:
- Locked jaw in tetanus
- Prolapse of third eye lid in tetanus in equines
- Absence of borborygmi (normal gut sound) in colic
Recovery
Recovery may be complete or incomplete.
Relapse
Relapse is the recurrence of a disease after a clinical cure. This usually occurs due to under dosing. This can occur both in infectious and non infectious diseases.
Example of relapse are:
- In salmonellosis: course of the antibiotic treatment is for 7 to 10 days but animal shows signs of recovery at 5 days and client will not bring his animal to clinic. Now salmonella organisms take an upper hand again causing the relapse of the disease. Due to resistance developed, and this relapse will not respond to the same antibiotic treatment.
- In milk fever: if inappropriate dose of calcium is given, then there will be relapse. Normally calcium at 8 to 12 gram per animal is required but animal shows immediate response when 1⁄2 bottle (450ml) is given but if remaining 1⁄2 is not given, then next day animal again becomes recumbent.
Complications
In some cases, primary disease causes a weakness of the body which then becomes susceptible to other diseases.
Examples of Complications are: Secondary pneumonia due to Bordotella bronchiseptica or Pseudomonas species in canine distemper.
Convalescence
Convalescence is the state through which a patient passes after a prolonged illness till it regains normal health and optimum power of production. After a period of prolonged illness it takes considerable time to regain its vitality. For this reason, adequate nutrition fortified with vitamins is required to sustain the loss of a patient following recovery from an acute bacterial infection where it was under the regime of long term antibiotic therapy.
Sequele
Sequele is the clinical outcome which may arise after the recovery from the disease.
Examples of Sequele are:
- FMD: Panting, Hypertrichosis
- CD: Repeated involuntary twitching of group of muscles which is called as myoclonic jerks, this due to loss of some neural impulse transfer
Death
Death is the complete cessation of respiration without any response to the external stimuli. Clinical death is characterized by depression of CNS activity. This stage is called as somatic death but the molecular life in the tissues is viable for about 5 to 6 minutes and these changes are reversible. After this stage molecular stage ensures.
Signs of death are:
- Cessation of respiration
- Cessation of circulation
- No response to external stimuli
- Dilation of pupil and fixation eye ball
- Fall of body temperature
- Setting up of rigor mortis
