The study of parasite-hosts and the relationship between them is known as Parasitology. The scope of parasitology is determined by the way they live rather than the organism or environment in the biological discipline. Parasites decrease host fitness by general or particular pathology and also affect the human body in different ways; through the oral route, skin, arthropod vectors, or sexual contact. Diagnosis of parasitic diseases depends on several laboratory methods like imaging techniques and endoscopy etc.    

Types of parasitology:                

1. Veterinary Parasitology         
2. Structural Parasitology                      
3. Quantitative Parasitology      
4. Molecular Parasitology
5. Medical Parasitology 

Infectious Diseases: Study of Infectious diseases, also known as Infectiology, is the medical specialty dealing with the diagnosis and treatment of complex infections. A particular type of antimicrobial action depends on the organism that causing infection:

1. Bacterial infections are treated with antibiotics,
2. Viral infections are treated with antiviral agents, and
3. Antifungal agents treat fungal infections.

Infectious diseases are highly rich in extraordinary actions which have a major impact on humankind. The successful diagnosis, prevention, and treatment of a wide range of infectious diseases have distorted the very fabric of society, providing important social, economic, and political benefits.