**3. Other controls for giardiasis**

This drug, initially explored in the equine species, was indicated in horses for the treatment of equine protozoal myeloencephalitis (EPM) caused by *Sarcocystis neurone* [11, 21, 22]. In recent

The mechanism of action is to inhibit the enzyme pyruvate ferredoxin oxidoreductase (PFOR), disrupting the metabolism of the parasite; in addition, this mechanism prevents the transference of electrons preventing energy metabolism by the parasite [17]. In helminths, it inhibits

As far as pharmacokinetic data are concerned, they are well known in equines, where after oral administration, it is absorbed and transformed into tizoxanide (deacetyl-nitazoxanide); the maximum level is reached at 2–3 h; in humans, it is reached at 4 h, 99% of which is bound to plasma proteins [39], excreted by urine and bile, in the form of glucuronic acid [11, 22].

This drug is a prodrug, followed by its rapidly hydrolyzed administration to its active metabolite, tizoxanide, 99% of which binds to blood plasma proteins [39]. Peak concentrations are observed for 1–4 h after administration. It is excreted in the urine, bile, and feces [12]. Its mechanism of action is by the inhibition of tubulin in helminths [11]. In the case of protozoa, electron and biochemical resonance studies have shown that pyruvate ferridoxin oxidoreductase (PFOR) and, to a lesser extent, hydrogenase reduce ferredoxin, which is oxidized by the nitro group in position 5 over the nitroheterocyclic compounds such as nitazoxanide [39]. In these organisms, nitazoxanide is reduced to a toxic radical in an organelle of carbohydrate metabolism and the hydrogenosome which contains hydrogenase PFOR

After oral administration in horses, nitazoxanide is absorbed and rapidly converted to tizoxanide (deacetyl-nitazoxanide). Nitazoxanide levels are reached within 2–3 h and are not detectable 24 h after dosing, which is 99% bound to proteins and is metabolized in the liver and is excreted in urine, bile, and feces; glucuronic acid is the conjugation of the compound [39, 44]. Adverse effects are commonly reported, such as fever, anorexia, reduced appetite, lethargy, and depression (Rodríguez García et al., 2004, Delgado et al.). However, the reproductive safety of nitazoxanide has not been determined in pregnant females; it is categorized as drug B by the FDA, not used during gestation or lactation, and it has been considered that the LD

The recommended dosage for canines is 10 mg/kg every 24 h for 3 days [26]; in a study published by Cabrera and Molina, effectiveness found at 8 days of treatment was 43.75%, which increased at 30 days of treatment with 87.5% [45]. This finding differs from those found by other authors such as Moron-Soto et al. and other authors consulted [42, 46, 47], and totally contradictory with respect to human pediatric patients, where the effectiveness is 80% [48, 49].

In humans, one of the drugs of choice for protozoal infections is teclozan, which is a derivative of dichloroacetamide; its trade name is known as Falmonox® (Sanofi-Aventis®, Paris, France)

years, it has been explored in the canine species for the treatment of *G. intestinalis* [42].

the polymerization of tubulin in the parasite.

140 Current Topics in Giardiasis

and ferredoxin [13, 15, 43].

50 is 10 g/kg [11, 22, 39].

**2.7. Teclozan**

There are vaccines for the control of Giardiasis of Fort Dodge© Animal Health for giardia, called Giardia-Vax® for dogs and Giardia Fel-O® for cats, their effectiveness being questionable [2, 51]. It has been considered that their application according to the commercial house, should be done after 4 months of life, and repetitions every 4–6 months, which makes its use in third world countries, is not very useful, if we consider epidemiological data on the prevalence of parasites in America Latin American countries, which can reach 27%, with high prevalences such as those in Brazil and Argentina that are above 20% (prevalence). This is why the use of the Giardia-Vax® vaccine in Latin America has had little impact on the control of the disease.

In human medicine, a combination of nutritional intervention and phytotherapy is the first line of approach for the treatment of giardiasis, whereas in veterinary medicine, dietary manipulation is often combined with antiprotozoal chemotherapy. Another point to consider is the use of probiotic therapy which could be useful in preventing infection or as an adjunct to the treatment of it; in this vein, the use of commensal bacteria can determine the vulnerability and the resistance to Giardia infection in mice. The use of probiotic lactobacilli releases a low molecular weight thermosensitive factor that inhibits the proliferation of Giardia trophozoites in in vitro culture. These modern therapeutic strategies justify further investigation which could prove to be more applicable and useful than drugs for the treatment in endemic regions [8, 52].

In any case, part of the control of the agent is to improve sanitary conditions, avoid contamination of water and food with cysts of the parasite, and control of more frequent parasites in hostile environments, that is, deworming programs every 3–4 months, especially for the canine species, with effective products such as benzimidazoles and especially fenbendazole and in particular the hygiene of pets with the use of baths with detergent products based on chlorhexidine, irgasan, and benzoyl peroxide (**Table 1**).


**Table 1.** Drugs used in canines and felines for the treatment of giardia intestinalis.
