Page 1087 - Clinical Small Animal Internal Medicine

110 Coccidia 1025

Table 111.2 Treatment of enteric coccidiosis in dogs and cats recover from Cystoisospora spp. infections have species‐
VetBooks.ir Antiprotozoal agent Treatment regimen specific immunity, but remain susceptible to infection
with other Cystoisospora spp. infections. For example, a

Ponazuril a 20 mg/kg PO twice 1–7 days apart OR puppy that acquires a C. canis infection and recovers
remains susceptible to infection with C. ohioensis.
50 mg/kg PO once While patients with coccidiosis respond to appropriate
Sulfadimethoxine b 50–60 mg/kg PO daily for 5–20 days therapy, untreated infections can lead to death from
Trimethoprim‐ 15–30 mg/kg PO every 12–24 hours for dehydration.
sulfonamide c 5 days
Amprolium d 300–400 mg PO daily for 5 days (canine) Public Health Implications
60–100 mg PO daily for 7 days (feline)
Furazolidone 8–20 mg/kg PO every 12–24 hours for Due to the species specificity, Cystoisospora spp. of dogs
5 days and cats are not zoonotic to humans.
a Ponazuril is coccidiocidal and may be superior to other drugs.
b Sulfadimethoxine is the only approved drug for treatment of
coccidiosis in the United States. Cryptosporidium spp.
c Trimethoprim‐sulfonamide combinations may cause acute hepatic
necrosis, keratoconjunctvitis sicca, macrocytic anemia, and type III Epidemiology/Pathophysiology
hypersensitivity reactions.
d Amprolium can cause anorexia, depression, diarrhea, and CNS There are many species of Cryptosporidium that infect a
disease due to induction of thiamine deficiency. wide range of hosts, including dogs and cats. This genus
PO, by mouth (per os).
is considered by some parasitologists to be more closely
related to a group of the Apicomplexa known as the gre-
Symptomatic therapy begins by withholding food garines, which infect mostly invertebrates. Recently,
initially, followed by small, frequent meals with a bland gregarine‐like stages have been described in multiple
diet once symptoms diminish. A class of medications Cryptosporidium spp. This may lead to a reclassification
commonly utilized to treat coccidiosis are the sulfona- of this genus in the future, and could possibly explain
mides, which may be potentiated for better efficacy. why most of the medications effective against coccidia
Sulfadimethoxine is labeled in the US for dogs with bac- are ineffective against Cryptosporidium spp.
terial enteritis associated with coccidiosis. Sulfonamides The major host of C. canis is the dog; for C. felis,
block folic acid synthesis and are effective against the the major host is the cat. Unlike Cystoisospora spp.,
schizont, an asexual stage. Sulfonamides are coccidio- Cryptosporidium spp. are not host specific, although dog
static, therefore fecal analysis may remain positive for and cat Cryptosporidium spp. tend to favor the major
oocysts during the course of therapy. Toxicity with use of host. This is an important distinction as other species,
sulfonamides has been reported and includes crystallu- such as C. parvum, can be zoonotic. The life cycle is sim-
ria, renal toxicity, keratoconjunctivitis sicca, type 3 ilar to that of Cystoisospora. The oocyst that is infective
hypersensitivity disorders, acute hepatic necrosis, and to the host contains four sporozoites that are not con-
hematopoietic disorders. Dobermans are at increased tained within sporocysts. The sporozoite will penetrate
risk for immune‐mediated complications. the host epithelial cell where trophozoites undergo
Ponazuril, a medication used to treat equine protozoal schizogony to form merozoites. These merozoites will,
myeloencephalitis, has recently gained popularity as an in turn, invade other epithelial cells and undergo another
off‐label treatment for canine and feline coccidiosis. The round of schizogony. This is followed by the sexual
mechanism of action is incompletely understood. A key phase, or gametogony, where microgametocytes are pro-
improvement over previous treatments is that ponazuril duced, fuse, and form zygotes. Zygotes can ultimately
is coccidiocidal rather than coccidiostatic, and fecal form either a thick‐walled oocyst that is infective (sporu-
flotation can be negative 1–2 days post treatment. lated) when it leaves the host, or a thin‐walled oocyst
Amprolium, another coccidiostat, has also been used for that remains within the host and leads to autoinfection.
canine and feline coccidiosis. It is a competitive inhibitor Pathologic changes occur when epithelial cells are
of thiamine and is most effective against the first‐genera- damaged by emerging stages. Malabsorption ensues, and
tion schizont. diarrhea is the primary clinical presentation. The sever-
ity of the infection is limited by developing immunity.
Infection can be self‐limiting if a host has a competent
Prognosis
immune system. However, clinical disease may be pro-
Prognosis following proper diagnosis and treatment of longed in dogs and cats with a compromised immune
canine and feline coccidiosis is good. Patients who system.