332 



SARCOCYSTIS, TOXOPLASMA AND RELATED PROTOZOA 



it is hardly likely that dogs are exposed 

 to such enormous numbers of parasites, 

 they considered that canine toxoplasmosis 

 is most frequently subclinical or asymp- 

 tomatic. They believed that the chance of 

 dogs spreading the disease to man under 

 ordinary circumstances is small. On the 

 other hand, Cole et al. (1953), in a study 

 of 37 people in a household containing 

 ro.vo/)/rtS»;a-infected dogs, found that the 

 sera of 9 of them were serologically pos- 

 itive and 5 of them ranged in titer from 

 1:80 to 1:1024. Of these 5 persons, 2 had 

 toxoplasmic encephalitis and neuroretin- 

 itis, while 1 had Toxoplas))ia parasitemia. 

 Makstenieks and Verlinde (1957) found 

 evidence of concurrent infection in man 

 and cats or dogs in a number of house- 

 holds in the Netherlands. These results 

 suggest that there is a relationship be- 

 tween toxoplasmosis in man, dogs and 

 cats, altho there is no proof of commun- 

 icability. 



Kimball et al. (1960) found that 44% 

 of their obstetrical patients who had lived 

 on farms were positive to the dye test as 

 compared with only 21*^^0 of those who had 

 never lived on farms. They observed a 

 significant association between a positive 

 dye test and contact with farm animals 

 (cattle, chickens, ducks and geese), and 

 suggested that domesticated fowls may be 

 an important source of human Toxoplasma 

 infections. 



febrile, non- febrile or subclinical. In the 

 first, the onset may be acute, with chills 

 and fever, or gradual. The temperature 

 may last for 2 to 4 weeks or even longer. 

 The lymph nodes are enlarged, the throat 

 is often sore, and the patients suffer from 

 malaise. Fatigue may persist for some 

 time following recovery, and the lymph 

 nodes remain enlarged for months. 



The main characteristic of the non- 

 febrile form is lymphadenitis. Its course 

 is benign, but the lymph nodes remain en- 

 larged for months. In the subclinical 

 form, the only characteristic is the pres- 

 ence of swollen but not tender lymph nodes. 



The second type of acquired human 

 toxoplasmosis is a typhus-like, exanthema- 

 tous disease. In addition to the exanthema, 

 there may be atypical pneumonia, myo- 

 carditis and meningoencephalitis, and the 

 termination is often fatal. Lymphadeno- 

 pathy may or may not be present. 



The third type is a cerebrospinal 

 form, characterized by fever, encephali- 

 tis, convulsions, delirium, lymphadeno- 

 pathy and a mononuclear pleocytosis, 

 followed by death. This form is quite rare. 



The fourth type is an ophthalmic form, 

 characterized by chronic chorioretinitis. 

 Hogan (1950) described ocular toxoplas- 

 mosis in detail. 



Pathogenesis : Toxoplasmosis may 

 vary from an inapparent infection to an 

 acutely fatal one. Asymptomatic toxo- 

 plasmiasis is the most common type. 



In man, the most common form of 

 the disease is the congenital type found in 

 newborn infants. It is characterized by 

 encephalitis, rash, jaundice and hepa- 

 tomegaly, usually associated with chor- 

 ioretinitis, hydrocephalus and micro- 

 cephaly, and the mortality rate is high 

 (Feldman, 1953; Feldman and Miller, 

 1956). 



Acquired (i.e., non-congenital) human 

 toxoplasmosis has many different manifes- 

 tations. Siim (1956) divided them into 4 

 main types. The most common is char- 

 acterized by lymphadenopathy. It may be 



Remington, Jacobs and Kaufman 

 (1960) reviewed toxoplasmosis in the 

 human adult. 



The disease in domestic animals is 

 similar to that in man. In dogs (cf. Cole 

 et al., 1953), the disease is most serious 

 in puppies altho adults may also die. 

 Signs include fever, cough, anorexia, 

 weakness, depression, ocular and nasal 

 discharges, pale mucous membranes, 

 dyspnea, premature birth and abortion. 

 The resistance of dogs to experimental 

 infection (Jacobs, Melton and Cook, 1955) 

 and the possible association of the disease 

 with distemper (Campbell, Martin and 

 Gordon, 1955) have already been mentioned. 



At necropsy, lesions of pneumonitis 

 are common. The liver may be swollen 



