**3.4** *Sappinia* **spp***.*

334 Non-Flavivirus Encephalitis

2001; Matin et al., 2008). However, in immunocompromised patients with an impaired cellular immune response, granuloma formation may be minimal or absent (Martinez and

Post mortem examination often shows severe edema and hemorrhagic necrosis. The amoebae colonize the brain tissue and produce subacute necrotising hemorrhagic encephalitis leading to brain dysfunction. *Balamuthia mandrillaris* trophozoites and cysts are present within the perivascular spaces and within the necrotic CNS parenchyma (Martinez and Visvesvara, 1997). The disease is likely to take a cutaneous route before secondarily attacking the CNS. The time period of transition from the cutaneous form to the CNS ranges from 30 days to 2 years, with an average of 5 –8 months (Bravo and Sanchez, 2003). The skin lesions may appear at the site of an abrasion of the skin surface of the patient, or lesions can appear as single or multiple plaques or nodules (Deetz et al., 2003). These plaques may appear on the face, the trunk or the limbs, with a rubbery to hard consistency (Bravo and Sanchez, 2003). Skin lesions indicate a

Because most of the cases of BAE have presented with no clear-cut clinical profile, they have been treated empirically with steroids as well as with antibacterial, antifungal and antiviral agents with almost no effect upon the course of the infection. Anti-inflammatory steroids that were administered may have actually facilitated spread of the infection by suppressing the inflammatory response. Two patients from California, a 60-year-old man, and a 6-year old girl, in addition to a 70-year-old woman from New York survived balamuthiasis after treatment with a combination of pentamidine isethionate, sulfadiazine, clarithromycin,

In the case of the Peruvian balamuthiasis patients with cutaneous lesions (Martínez et al., 2010; Bravo et al., 2011), one recovered without any treatment and two others became well after prolonged therapy with albendazole and itraconazole. The use of multiple antimicrobials in treatment makes it difficult to single out one or more of the drugs that might be the basis for optimal therapy. Furthermore, drugs may show synergistic activities in vivo that are not seen in in vitro testing. In vitro studies have shown that pentamidine and propamidine isethionates were amoebastatic but not amoebicidal. Among other drugs tested with little or no activity were macrolide antibiotics, azole compounds, gramicidin, polymyxin B, trimethoprim, sulfamethoxazole, and a combination of trimethoprim-

sulfamethoxazole as well as amphotericin B (Maciver, 2007; Visvesvara et al., 2007).

Recent information based on in vitro data has shown that miltefosine was able to lysed the amoebae. Voriconazole, however, had virtually no effect on *Balamuthia* (Maciver, 2007; Visvesvara et al., 2007). Given the problems with the diagnosis of infection and the lack of

Few patients have survived PAM. One of these survivors, a Californian girl, was aggressively treated with intravenous and intrathecal amphotericin B, intravenous and intrathecal miconazole, and oral rifampin [2, 28]. Over a 4- year follow-up, she remained completely healthy and free of any neurological deficits. It was believed that amphotericin B and miconazole had a synergistic effect but that rifampin was without effect on the amoebae. Based on *in vitro* testing and *in vivo* mouse studies, amphotericin B was reported to be more effective against *Naegleria* than amphotericin B methyl ester, a water-soluble form of the drug. *In vitro* studies of phenothiazine compounds (chlorpromazine and trifluoperazine), which can accumulate in the CNS, were found to have inhibitory effects on

Visvesvara, 1997; 2001).

**3.3** *Naegleria fowleri* 

site of entry and are frequently observed in BAE patients.

fluconazole, and flucytosine (5-fluorocytosine) (Deetz et al., 2003).

effective antimicrobial agents, the prognosis for patients is poor.

As it has been recently reported as pathogenic to humans and other animals, no studies have been carried out so far regarding therapy and prognosis of this amoeba.


Encephalitis Due to Free Living Amoebae: An Emerging Issue in Human Health 337

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Bravo FG, Alvarez PJ, Gotuzzo E. (2011). Balamuthia mandrillaris infection of the skin and

Deetz TR, Sawyer MH, Billman G, Schuster FL, Visvesvara GS. (2003).Successful treatment

Gelman BB, Rauf SJ, Nader R, et al. (2001) Amoebic encephalitis due to Sappinia diploidea.

Heggie TW (2010) Swimming with death: Naegleria fowleri infections in recreational waters.

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Maciver SK.(2007). The threat from Balamuthia mandrillaris. Journal of Medical

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Table 1. Characteristics of FLA as causal agents of encephalitis (adapted from Visvesvara et al., 2007).

#### **3.5 Novel therapeutic approaches**

Recently, the application of siRNA in *Acanthamoeba* species (Lorenzo-Morales et al., 2005; 2008; 2010) has opened a novel approach for the progress of future therapies based on siRNAs alone or in combination with chemical compounds. Also the use of RNAi moleculaes could be very powerful for the identification of novel drug targets and metabolic pathways in these pathogens that could be exploited for the development of new therapeutic agents. Recently, RNAi methodology has been successfully use in *Naegleria fowleri* (Jung et al., 2008) resulting in a reduced pathogenicity of the RNAi-treated amoebae. Therefore, RNAi molecules are currently presenting as very powerful tools that are waiting to be fully exploited in the development of new therapies against pathogenic FLA.
