Pathogens and Diseases
நோய்க்கிருமிகள் மற்றும் நோய்கள்
Pathogens do not just invade; they hijack host machinery to replicate. If you think infection is merely 'getting sick,' you are failing the basics of host-parasite interaction. Remember, every pathogen is an evolutionary strategist aiming for survival at your expense.
The idea
Pathogens include bacteria, viruses, fungi, protozoans, and helminths. These organisms enter the host body, multiply rapidly, and interfere with vital physiological activities. This interaction results in morphological and functional damage to the host tissues. The severity of the disease depends on the pathogen's virulence and the host's immune response.
Why it matters
Parasitic organisms evolve to exploit host resources for their own survival and reproduction, which inadvertently harms the host.
NEET lens
NEET focuses on the classification of pathogens and their specific modes of damage. Expect matching-type questions linking the pathogen to its taxonomic group. Do not confuse the causative agent with the vector. Memorize the specific examples provided in the NCERT table to secure marks.
Clinical significance
When pathogens breach the immune system, they induce systemic damage, often leading to organ failure or chronic inflammation. For instance, Salmonella typhi causes structural damage to the intestinal mucosa, leading to perforation. Understanding this mechanism is vital for diagnosing pathology in clinical practice.
Introduction
Pathogens are disease-causing organisms — bacteria, viruses, fungi, protozoans and helminths. They enter the body, multiply and interfere with normal functions.
Core concept
Common diseases (NCERT): Typhoid — Salmonella typhi (bacterium); spreads through contaminated food/water; sustained high fever (39-40°C); confirmed by Widal test; the cook Mary Mallon ('Typhoid Mary') spread it. Pneumonia — Streptococcus pneumoniae and Haemophilus influenzae; infects alveoli, which fill with fluid; lips and finger nails may turn grey to bluish. Common cold — rhinoviruses; nose and respiratory passage, not lungs. Malaria — Plasmodium; female Anopheles. Amoebiasis (amoebic dysentery) — Entamoeba histolytica; large intestine; houseflies are mechanical carriers. Ascariasis — Ascaris (roundworm); eggs in soil and water; internal bleeding, blockage of intestinal passage. Filariasis (elephantiasis) — Wuchereria (W. bancrofti, W. malayi); female Culex mosquito; chronic inflammation of lymphatic vessels of lower limbs. Ringworm — fungi Microsporum, Trichophyton and Epidermophyton; dry, scaly lesions on skin, nails and scalp; favoured by heat and moisture.
Go deeper
Prevention: personal hygiene (clean water, food), public hygiene (proper disposal of waste, cleaning of water reservoirs), controlling vectors (mosquitoes) and their breeding places, e.g. introducing Gambusia fish that feed on mosquito larvae.
From Class 10
Diseases like cold, typhoid and malaria are caused by different microbes. Knowing the microbe tells you how the disease spreads and how to stop it.