Use the CDC website to examine giardiasis surveillance data. Notice the variety of transmission modes that have been identified. The CDC notes several characteristics that make drinking and recreational water and person-to-person contact ideal modes of transmission. Which of the following contributes to the ease of transmission via these modes? 1) Resistance to antibiotics
2) Low infectious dose
3) Survival in environment outside host
4) Resistance to chlorine treatment

The option that contributes to the ease of transmission is 2 ( Low infectious dose).

Explanation:

Giardiasis is an infection that affects the intestine which is caused by a parasite known as giardia intestinalis. The giardiasis surveillance data recorded by the CDC, was done to educate public health practitioners and health-care providers about the scope and magnitude of giardiasis. It also provided different route through which the parasite can be transmitted to uninfected individual and these include:

--> Waterborne transmission: In this route of transmission, an individual becomes infected when they drink contaminated water from recreational water(pools) or streams.

--> Foodborne transmission: In this route of transmission, an individual becomes infected when they eat contaminated uncooked foods or foods that become contaminated after cooking.

--> Person to person: in this route of transmission, a healthy individual becomes infected through ianal sex practice.

The LOW INFECTIOUS DOSE of the parasite contributes to the ease at which transmission occurs through the above mentioned routes. The parasite has a two stage life cycle, the trophozoite and cyst. Ingestion of as few as 10 cysts can lead to giardiasis Infection.

chordata is the answer