Parasites and Vectors in Microbiology Parasites are organisms that live on or inside a host, deriving nutrients at the host’s expense. Vectors are organisms, typically arthropods, that transmit parasites or pathogens between hosts. Parasites Definition: Types of Parasites: Vectors Definition: Types of Vectors: Parasite-Vector-Host Relationship Life Cycle of Parasites Roles of Vectors: Important Parasitic Diseases and Vectors Disease Causative Parasite Vector Mode of Transmission Malaria Plasmodium species Anopheles mosquito Bite