Toxoplasmosis (Toxoplasma gondii)

Parasite present in meat, food, water, soil, or poop of infected animals, i.e., cat, is the major cause behind Toxoplasmosis. 

How it spreads : Consuming undercooked meat, shellfish, or direct contact with cat poop can result in the infection. Meanwhile, cats get infected after eating infected birds, rodents, or small animals. Finally, drinking contaminated water and polluted food could be the reason for developing an infection. But, it mostly happens when people don't wash their hands after petting, feeding the animals, or, more importantly, cleaning the litter box. 

Who is at risk : People with weak immune systems are at higher risk of getting infected with this disease. Additionally, pregnant women may transfer the infection to their unborn child, resulting in congenital disabilities or complications. 

Signs in cats : Cats infected with Toxoplasmosis usually don't show any signs or rarely appear sick.  

Symptoms in people : Mild flu-like or eye diseases may rarely appear in the infected people. But most of the time, signs don't appear in people with Toxoplasmosis. Thus, there can be severe complications in people with weak immune systems.