Yes, it is perfectly normal for parasitic diseases’ symptoms to successively come and go. For instance, some parasitic diseases can alternate between different symptomatic and asymptomatic phases. For instance, people suffering from malaria caused by the protozoan parasite Plasmodium will typically suffer from relapses of the symptoms separated by many months if they are not treated.
Many parasites are also able to remain asymptomatic for many months or even years within the body. These parasites usually caused mild flu-like symptoms in the days following the primary infection. However, it is usually impossible at this stage to know that it is actually a parasitic infection, as these symptoms are widespread and unspecific. These mild flu-like symptoms will resolve quickly by themselves. Then, the parasite can hide itself within the body without causing any symptom for a more or less long period of time. As a matter of fact, scientists estimate that asymptomatic parasite carriers are more widespread than what we previously thought. Following that asymptomatic stage, it is possible that the parasite never cause any symptom at all. However, it is also possible that the parasite will be reactivated and that the person will eventually suffer from the normal symptoms associated with this specific parasitic disease. This type of situations usually happens when the immune status of the host changes, meaning that the immune system of the host is not able to deal with the parasite anymore leading to its proliferation. It usually happens when the host become affected with other sicknesses, such as cancer or other infections like AIDS.
The reactivation of the parasite after an asymptomatic period could also happen in the normal course of the infection. For example, people infected with the nematode Dracunculus medinensis responsible for the guinea worm disease are usually asymptomatic for approximately one year as the parasite maturates in the host’s body. However, when the worm is fully matured, it wants to go out of the body in order to release larvae to fulfill its life cycle. It is when the worm migrates to the lower leg and goes out of the body through the skin that the infected person experiences symptoms usually associated with this infectious disease like burning pain and swelling.
Furthermore, other parasitic diseases typically have different phases with different symptoms. Chagas disease and the sleeping sickness, both caused by different species of the parasite Trypanosoma, are good examples of parasitic diseases with different symptoms depending of the stage of the disease. Interestingly, in the case of Chagas disease, 30 to 40 % of the infected people will develop a later stage of the illness 10 to 30 years after the primary infection.
Finally, in some rare cases, symptoms can appear later in life even when the parasitic disease was cured. This is the case with the successfully treated visceral manifestations of the parasite Leishmania. Patients are at risk to develop a post-leishmaniasis skin manifestation called post-kala-azar dermal leishmaniasis months or even years after being successfully treated. This manifestation is quite common, as it occurs in about 50 % of the cases in some African countries and in 5 to 10 % of the cases in India. The differences between countries is explained by the presence of different species of Leishmania.
Source: Centers for Disease Control and Prevention
