Because they are more vulnerable to any infection.
Anyone can be infected by T. gondii, but usually only those individuals with weakened immune systems (immunocompromised) develop symptoms of the disease. For them, toxoplasmosis can be severe, debilitating, and fatal.
The prognosis for acquired toxoplasmosis in adults with strong immune systems is excellent. The disease often disappears by itself after several weeks.
An opportunistic infection (OI) is an infection that occurs only when the host's defense systems (ie, the immune system) are weakened. The common characteristic of all agents that cause opportunistic infections is that they rarely affect individuals with healthy immune systems. For example, the disease AIDS (acquired immunodeficiency syndrome) is a classic cause of immune system depression and is associated with many opportunistic infections, including toxoplasmosis, pneumocystis pneumonia (PCP), and others.
The parasite commonly transmitted from animals to humans through contact with contaminated feces is Toxoplasma gondii. This parasite can be found in the feces of infected cats and can be acquired by humans through contact with contaminated soil or unwashed vegetables. It can lead to toxoplasmosis, a disease that can be especially harmful to pregnant women and individuals with weakened immune systems.
Actually I also did not know the meaning. But after searching a few minutes I got it, the answer is Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii. The parasite infects most genera of warm-blooded animals.
People who have toxemia are often susceptible to infection because their immune systems are weakened
Most individuals who contract toxoplasmosis do not require treatment because their immune systems are able to control the disease. Symptoms are not usually present. Mild symptoms may be relieved by taking over-the-counter medications
Live attenuated vaccines are typically not given to people with compromised immune systems because they contain weakened forms of the virus that may still cause illness in those with weakened immune responses.
When Aspergillus does cause disease, however, it usually occurs in those individuals with weakened immune systems
Oral candidiasis typically occurs in people with abnormal immune systems.
Their immune systems were not used to diseases, as there weren't a lot of diseases at the time.
Once infected, an individual is immune to reinfection.