NO. IO COCKROACHES—ROTH AND WILLIS 25 
The anthrax bacillus can multiply in the intestine of Blatia orien- 
talis (Cao, 1898). Kiister (1903) reported data suggestive of multi- 
plication of anthrax bacilli in the gut of B. orientalis. There was an 
inverse relation between the number of days the anthrax bacillus 
remained in the cockroach’s gut and the infection time in hours after 
injection into mice: 6 days/104 hours, 12 days/41 hours, 15 days/36 
hours, and 16 days/24 hours. This is based on the assumption that 
an increase in the number of micro-organisms shortens the infection 
time. Cao (1898, 1906) found that certain bacteria (e.g., “Bacillo 
similcarbonchio” and “Bacillo proteisimile”) isolated from the oriental 
cockroach were pathogenic for guinea pigs. Continued passage 
through the cockroaches and variation in diet increased the virulence 
of these and other originally nonpathogenic bacteria. Ekzempliarskaia 
(in Pavlovskii, 1948) also found that the virulence (to guinea pigs) 
of Mycobacterium avium and Mycobacterium piscium increased after 
the bacteria passed through the intestine of Blatta orientalis. Moiser 
(1946, 1946a) stated that Mycobacterium leprae is found in such 
numbers in cockroaches that have fed on leprous nodules as to sug- 
gest multiplication in the body of the insect. 
V. FUNGI 
Two fungi, Aspergillus fumigatus and Aspergillus niger, which 
are sometimes found associated with pathological conditions, have been 
found naturally in cockroaches. Geotrichum candidum was success- 
fully inoculated into a cockroach, but Histoplasma capsulatum was 
not recovered in feces after feeding experiments. An annotated list 
of these organisms is given in Appendix C. These observations ap- 
parently cover the field. Yet a very large number of fungi are asso- 
ciated with insects (Steinhaus, 1946) ; for this reason, the dearth of 
information about pathogenic fungi that may possibly be associated 
with cockroaches is particularly surprising. This might be a fertile 
field for further study. 
About 40 species (mostly Laboulbeniales) of nonpathogenic fungi 
and about 6 yeasts have been found on or in cockroaches. These are 
not discussed. 
VI. PROTOZOA 
Only four protozoa pathogenic to man have been reported to be as- 
sociated naturally or experimentally with cockroaches (Appendix D), 
in contrast to many nonpathogenic forms. The pathogenicity of three 
of these, Balantidium coli, Entamoeba histolytica, and Giardia in- 
testinalis, is unquestioned, but that of the fourth, Trichomonas 
hominis, is doubtful. 
