Disease Vectors and Pathogens

When children play barefoot in pools of dirty water and flood water, they may suffer from Leptospirosis and bilharzia. 

A parasite depends on its host to stay alive. Killing the host before the reproduction destroys parasite also as it needs host to produce its progeny generation after generation. This makes option D correct. In order to keep the host alive to produce many generations of parasite offspring, it is necessary for a parasite to become less virulent or gentle over many generations. This makes option A incorrect. Fast reproduction produces increase the number of parasite offspring but poses extra burden on host and makes the host survival harder. This makes option B incorrect. Similarly, sticking too long to a host decreases its survival chances and hence, parasite keeps switching the host over time. Option C is incorrect. Thus, the correct answer is option D.

Arceuthobium is the genus of parasitic plants. The host of this plants are members of Pinaceae and Cupressaceae. The stem is reduced and the leaves are minute structures. The flowers are sessile. Most of the parasitic plant is covered beneath the bark of the host plant. 

There are harmful and toxic chemicals present in the mosquito repellents and coils like the pyrethrum. These molecules when inhaled may cause diseases like asthma, bronchitis and another type of chronic lung infections. These are collectively referred as the bronchial diseases. 

Sir Ronald Ross discovered the malarial parasite in the gastrointestinal tract of mosquito and led to the realization, that malaria was transmitted by mosquitoes. He received the Nobel Prize in 1902 for his work on malaria. 
Thus, the correct answer is option C.

Explanation: Cholera is spread through intake of contaminated water or food in places that lack adequate sanitation facilities.

Monocystis is an endoparasite in the seminal vesicle and coelom of earthworms. It belongs to order of Gregarinida. Monocystis is a monogenetic parasite, which means its life cycle is completed in a single host that is earthworm. Hence, option A is correct.

Haemophilia is a group of hereditary disease that impair the body's ability to control blood clotting or coagulation. Britain's Queen Victoria, through two of her five daughters, passed this mutation to various royal families across the continents, including the royal houses of Spain, Germany and Russia. Victoria's son also suffered from this disease. For this reason, Hemophilia is also called as 'the royal disease'.
Thus, the correct answer is option (D), 'Both (B) and (C)'.

A plant which depends on its host for only water and nutrients, but not sugars is a partial parasite. They do not depend on the host for food as they are usually chlorophyllous, so they are able to photosynthesize. 

A. The largest root parasite is rafflesia because rafflesia blooms the largest flower grows to be 3 ft across and almost 50 pounds. The only visible parts of this parasite are usually its flower.

The Rickettsiae are a diverse group of bacteria some of which can be transmitted to humans via the bites of fleas, lice, ticks or mites. Several Rickettsia species present in Australia are capable of causing disease in people. 
Syphilis is a bacterial infection usually spread by sexual contact. The disease starts as a painless sore typically on your genitals, rectum or mouth. Syphilis spreads from person to person via skin or mucous membrane contact with these sores.
Trichinosis (trik-ih-NO-sis), sometimes called trichinellosis, is a type of roundworm infection. Roundworm parasites use a host body to live and reproduce. Occurring primarily among meat-eating animals (carnivores) especially bears, foxes and walruses the infection is acquired by eating roundworm larvae in raw or undercooked meat. 
An analgesic, or painkiller, is any member of the group of drugs used to achieve analgesia relief from pain.  Analgesic drugs act in various ways on the peripheral and central nervous systems. They are distinct from anesthetics, which reversibly eliminate sensation. Analgesics include paracetamol, the non-steroidal anti-inflammatory drugs (NSAIDs) such as the salicylates, and opioid drugs such as morphine and oxycodone.
Gentamicin is an aminoglycoside antibiotic composed of a mixture of related gentamicin components and fractions and is used to treat many types of bacterial infections, particularly those caused by Gram-negative organisms.
Neomycin is an aminoglycoside antibiotic found in many topical medications such as creams, ointments, and eyedrops. The discovery of neomycin dates back to 1949. It was discovered in the lab of Selman Waksman, who was later awarded the Nobel Prize in Physiology or Medicine in 1951. Neomycin belongs to aminoglycoside class of antibiotics that contain two or more aminosugars connected by glycosidic bonds. 

Quinine is one of the most important drugs known and it is the only adequate cure for Malaria and quinine is extracted from the hard thick bark of species of Cinchona.