Feline viral infections can lead to immunosuppression that predispose cats to other infections, such as protozoan diseases. More than one hundred cats coming from shelter houses and veterinary clinics were tested for detection of protozoan (Toxoplasma gondii and Neospora caninum) and viral infections (Feline immunodeficiency virus, Feline leukemia virus and Virus of feline panleukopenia) to analyse risk factors of co-infections for developing of clinical signs in naturally infected cats. Co-infection with protozoan diseases can lead to severe clinical signs and be even fatal in immunosuppressed cats. Results were statistically analysed to find risk factors of infections and occurrence of clinical signs. Cats with some infection showed clinical signs more often than cats without any infection. Clinical signs were noticed more often in cats with mixed infections than in cats with mono infections, and were noted as a more serious and acute in case of FIV and T. gondii co-infection. More details and statistical analysis to be seen inside!