Reservoir Host: Definition and Examples

Definition

• Reservoir Host: A host harboring a pathogen that naturally lives, grows, and reproduces without causing illness to the host.
• Synonyms: Natural reservoir, nidus, asymptomatic host.
• Comparison: Different from a paratenic host.

Characteristics

• Asymptomatic: Often shows no symptoms.
• Pathogen Spread: Disease may spread easily when a pathogen utilizes various reservoirs.

Types of Hosts

• Primary Host (Definitive Host): Where the symbiont is sexually active.
• Secondary Host (Intermediate Host): Hosts sexually immature stages.
• Reservoir Host: Generally asymptomatic carrier of a pathogen.
• Paratenic Host: Serves as transport for the parasite without development stages.

Types of Reservoirs

• Human Reservoirs: Humans can be both reservoirs and definitive hosts for diseases like STDs, measles.
• Animal Reservoirs: Include vertebrates and invertebrates, e.g., bats for coronaviruses.
• Environmental Reservoirs: Soil and water can harbor pathogens like Clostridium tetani.

Common Characteristics of Reservoir Hosts

• Sustainable Relationship: Pathogen can survive without harming the host.
• Immune System: A balanced immune response facilitates coevolution.
• Transmission Efficiency: Host species can transmit pathogens efficiently.

Examples of Reservoir Hosts

• Birds: Reservoirs of West Nile virus.
• Ticks: Source of bacteria like spotted fever rickettsiae.
• Rodents: Reservoir hosts for Lyme disease bacterium.
• Wild Waterfowl: Can transmit avian influenza to poultry.
• Human Carriers: Reservoirs for sexually-transmitted diseases.

Modes of Transmission

• Direct Transmission: Includes person-to-person, vertical, and environmental contact.
• Indirect Transmission: Involves airborne, waterborne/foodborne, fomite, and vector-mediated transmission.

Biological Importance

• Amplifying Transmission: Reservoir hosts allow pathogens to persist and transmit more effectively.
• Spillover Events: Pathogens can move from human reservoirs to other hosts, causing outbreaks.
• Impact on Health: Identifying reservoirs is crucial for disease control.

Role in Interventions

• Source for Pathogen Study: Provides samples for vaccine development.
• Understanding Immune Response: Insight into tolerance mechanisms.
• Studying Pathogenesis: Helps in finding therapeutic interventions.

References

• Various studies and articles on the biological and epidemiological aspects of reservoir hosts.