Hammondia hammondi Frenkel 1974

ETYMOLOGY: Hammondia after Dr. Datus M. Hammond and hammondi after Dr. D. M.

SYNONYMS: Toxoplasma hammondi [Frenkel, 1974] Levine 1977; Isospora hammondi

[Frenkel and Dubey, 1975] Tadros and Laarman, 1976. Hammondia hammondi was also refereed

to as the CR-4 strain of Toxoplasma gondii isolated by Frenkel and Dubey (1975A, 1975B) and

the WC1170 parasite of Wallace (1973).

HISTORY: The oocysts of this parasite are structurally indistinguishable from those of

Toxoplasma gondii. In 1971, Drs. Frenkel and Dubey isolated oocysts that were structurally

similar to T. gondii from a feral cat from Iowa. Dr. Wallace (1973) also isolated a similar

parasite from the feces of a feral cat from Hawaii. Inoculation of mice with these oocysts

produced large tissue cysts in skeletal muscles and very few tissue cysts in the brain. Both

groups of researchers demonstrated that the life cycle of the parasite is heteroxenous. Dr. Frenkel

first erected the Genus Hammondi and used the name H. hammondi in a review article on tissue

cyst forming coccidia (Frenkel, 1974). He and Dr. Dubey latter fully described the life cycle of

the parasite (Frenkel and Dubey, 1975a, 1975b). Because he published the name first (Frenkel,

1974) he is technically the author of the original name Hammondia hammondi and not he and

Dr. Dubey as is frequently cited.

GEOGRAPHIC DISTRIBUTION: Probably worldwide. Hammondia hammondi has been

found in Iowa and Hawaii in the United States (Frenkel and Dubey, 1975a, 1975b; Wallace,

1975), Germany (Rommel and Seyerl, 1976), Australia (Mason 1978) and Japan (Shimura and

PREVALENCE: The prevalence of infection in cats is low. Wallace (1975) found H. hammondi

in 3 of 1,604 cats in Hawaii. Christie et al. (1977) examined the feces form 1,000 cats in

Columbus, Ohio for H. hammondi. Nine cats were shedding oocysts which were the correct size

and shape for either H. hammondi or T. gondii. Two of these proved to be H. hammondi and 7

were T. gondii following mouse inoculation. Another isolate of H. hammondi was obtained from

a pooled sample from 175 cats by mouse inoculation.

PARASITE IDENTIFICATION: Oocysts of H. hammondi are excreted unsporulated in the

feces. The oocysts are colorless, subspherical to spherical, and measure 10.5-12.5 by 11.2-

13.2 &m (mean, 10.6 by 11.4 &m). Sporulated oocysts contain two ellipsoid sporocysts each

with 4 sporozoites. Sporocysts measure 6.0-7.5 by 8.0-10.7 &m (mean, 6.5 by 9.8 &m), lack

a Stieda body, and contain a sporocyst residuum composed of dispersed or compact granules.

The sporozoites are elongate and curved within the sporocyst had have a crystalloid body.

Sporulation occurs in 2 to 3 days at room temperature (22 to 26 C).

The similarity in oocyst size and structure between T. gondii and H. hammondi make

diagnosis based on oocyst structure alone impossible. Animal inoculation is needed for a

definitive diagnosis to be obtained. Identification of H. hammondi in tissues is also difficult. The

tachyzoites of T. gondii and H. hammondi are indistinguishable from each other. The tissue cysts

of H. hammondi resemble those of T. gondii and can be confused with sarcocysts of some thin-
C:\Aa Old D\Dwight\CATBOOK\complete\chap1\chap1-with figs.doc

Page 37 of 112

Feline Clinical Parasitology – Chapter 1

walled Sarcocystis species (Mehlhorn and Frenkel 1980).

LIFE CYCLE: Cats are the only know feline definitive hosts. However, other felids may be

suitable definitive hosts. The life cycle is obligatorily heteroxenous. Two types of schizonts are

found in the cats small intestines 4 and 5 days after tissue cysts are ingested. The sexual stages

first appear 5 days after infection. The prepatent period is 5 to 6 days and the patent period is 12

to 28 days. Inoculation of cats with H. hammondi oocysts does not lead to oocyst excretion or to

latent infections in their tissues.

Natural intermediate hosts include rats (Rattus rattus and R. norvegicus), goats (Capra

hircus), and roe deer (Capreolus capreolus). Experimental intermediate hosts include white

mice, deer mice, long-tailed field mice, yellow-necked field mice, rats, multimammate rats,

guinea pigs, hamsters, bank voles, European voles, field voles, dogs, goats, sheep, monkeys, and

pigs (Dubey, 1993). Chickens can not be infected with H. hammondi (Dubey and Streitel, 1976).

When an intermediate host ingests oocysts of H. hammondi, the oocysts excyst in the intestine

and liberate the sporozoites. The sporozoites penetrate the intestinal mucosa and multiply by

endodyogeny in the lamina propria, submucosa and muscularis, Peyer's patches and mesenteric

lymph nodes for about 11 days. Tissue cysts are present in the muscles of mice by 11 days. The

tissue cysts are initially small but can be over 300 &m in length in about a month. The tissue

cysts remain viable for 1.3 years and probably longer. Tissue cysts are not infective for

intermediate hosts. Congenital transmission of H. hammondi does not occur in mice (Dubey and

Streitel, 1976) or cats (Dubey, 1977).

PATHOGENICITY: Hammondia hammondi does not cause disease in cats. Mice inoculated

tracts of these mice and are due to multiplication of tachyzoites. A transient myositis may be

present in the skeletal muscles of infected mice.

IMMUNITY: Immunity to H. hammondi in cats is less stable than immunity to T. gondii.

About 50% of cats will re-excrete oocysts when challenged (Dubey, 1975). Some cats

will spontaneously re-excrete small numbers of oocysts in the absence of reinfection.

Immunosuppression of cats does not affect the course of a primary H. hammondi infection in

cats but does cause cats to re-excrete oocysts. Infection with H. hammondi does not make cats

immune to infection with T. gondii. Cats that have recovered from a H. hammondi infection do

not develop antibodies to T. gondii.

In contrast to cats, intermediate hosts that are inoculated with oocysts develop antibodies

that cross-react with T. gondii. This cross-reactive immunity is also protective against challenge

with pathogenic strains of T. gondii (Christie and Dubey, 1977; Dubey, 1978; 1981; Monday and

Dubey, 1988). Hammondia hammondi immune serum from mice recognizes all the major

surface antigens of T. gondii except the 21.5 kD antigen (Araujo et al., 1984). A monoclonal

antibody to the immunodominant p30 antigen of T. gondii also reacts with tachyzoites of H.

hammondi (Riahi et al., 1998). Immunization of hamsters with H. hammondi affords minimal

protection against challenge with Besnoitia jellisoni (Dubey, 1978).

HAZARDS TO HUMANS: Hammondia hammondi infection was attempted in 4 species

of nonhuman primates (Saguinus nigricollis, Macaca fascicularis, Macaca mulatta, and

Cercocebus atys) (Dubey and Wong, 1978). None of the monkeys developed clinical signs of

oocysts may suffer from up to 30% mortality. Lesions are present in the intestinal

C:\Aa Old D\Dwight\CATBOOK\complete\chap1\chap1-with figs.doc

Page 38 of 112

Feline Clinical Parasitology – Chapter 1

disease and H. hammondi was isolated from only Saguinus nigricollis. It is possible that humans

could serve as intermediate hosts. No recorded cases of human infection exist.

Araujo FG, Dubey JP, Remington JS. 1984. Antigenic similarity between the coccidian

parasites Toxoplasmagondii and Hammondia hammondi. J Protozool 31:145-147.

Christie E, Dubey JP. 1977. Cross-immunity between Hammondia hammondi and

Toxoplasma infections in mice and hamsters. Infect. Immunol. 18:412-415.

Christie E, Dubey JP, Pappas PW. 1977. Prevalence of Hammondia hammondi in the feces

of cats in Ohio. J. Parasitol. 63:929-931.

Dubey JP. 1975. Immunity to Hammondia hammondi infection in cats. J Am Vet Med

Dubey JP. 1993. Toxoplasma, Neospora, Sarcocystis, and other tissue cyst-forming coccidia

of humans and animals. In Parasitic Protozoa, Vol. 6., J.P. Kreier and J.R. Baker

(eds), Academic Press, Inc., San Diego, Calf. pp 1-158.

Dubey JP. 1977. Attempted transmission of feline coccidia from chronically infected

queens to their kittens. J Am Vet Med Assoc 170:541-543.

Dubey JP. 1978. A comparison of cross protection between BCG, Hammondia

hammondi, Besnoitia jellisoni and Toxoplasma gondii in hamsters. J Protozool 25:382-

Dubey JP. 1981. Prevention of abortion and neonatal death due to toxoplasmosis by

vaccination of goats with the nonpathogenic coccidium Hammondia

hammondi. Am J Vet Res 42:2155-2157.

Dubey JP, Steitel RH. 1976. Further studies on the transmission of Hammondia hammondi

in cats. J Parasitol 62:548-551.

Dubey JP, Wong M. 1978. Experimental Hammondia hammondi infection in monkeys. J

Parasitol 64:551-552.

Frenkel JK. 1974. Advances in the biology of sporozoa. Z Parasitenkd. 45:125-162.

Frenkel JK, Dubey JP. 1975a. Hammondia hammondi gen. nov., sp.nov., from domestic

cats, a new coccidian related to Toxoplasma and Sarcocystis. Z Parasitenkd 46:3-12

Frenkel JK, Dubey JP. 1975b. Hammondia hammondi: A new coccidium of cats producing

cysts in muscle of other mammals. Science 189:222-224.

Mason RW. 1978. The detection of Hammondia hammondi in Australia and the

identification of a free-living intermediate host. Z Parasitenkd 57:101-106.

Mehlhorn H, Frenkel JK. 1980. Ultrastructural comparison of cysts and zoites of

Toxoplasma gondii, Sarcocystis muris, and Hammondia hammondi in skeletal muscle of

mice. J Parasitol 66:59-67

Munday BL, Dubey JP. 1988. Prevention of Toxoplasma gondii abortion in goats by

vaccination with oocysts of Hammondia hammondi. Aust Vet J 65:150-153.

Riahi H, Bouteille B, Darde ML. 1998. Antigenic similarity between Hammondia hammondi

and Toxoplasma gondii tachyzoites. J Parasitol 84:651-653.

Rommel M, von Seyerl F. 1975. 1st demonstration of Hammondia hammondi (Frenkel and

Dubey 1975) in the feces of a cat in Germany. Berl Munch Tierarztl Wochenschr 89:398-

C:\Aa Old D\Dwight\CATBOOK\complete\chap1\chap1-with figs.doc

Page 39 of 112

Feline Clinical Parasitology – Chapter 1

Shimura K, Ito S. 1986. Isolation of Hammondia hammondi in Japan. Nippon Juigaku

Wallace GD. 1973. Sarcocystis in mice inoculated with Toxoplasma-like oocysts from cat

feces. Science 180: 1375-1377.

Wallace GD. 1975. Observations on a feline coccidium with some characteristics of

Toxoplasma and Sarcocystis. Z Parasitenkd 46:167-178.