Treatment with beta-cyclodextrin of natural Cryptosporidium parvum infections in lambs under field conditions

Past, current, and potential treatments for cryptosporidiosis in humans and farm animals: A comprehensive review

The intracellular protozoan parasite of the genus Cryptosporidium is among the leading causes of waterborne diarrheal disease outbreaks throughout the world. The parasite is transmitted by ingestion of infective oocysts that are highly stable in the environment and resistant to almost all conventional disinfection methods and water treatments. Control of the parasite infection is exceedingly difficult due to the excretion of large numbers of oocysts in the feces of infected individuals that contaminate the environment and serve as a source of infection for susceptible hosts including humans and animals. Drug development against the parasite is challenging owing to its limited genetic tractability, absence of conventional drug targets, unique intracellular location within the host, and the paucity of robust cell culture platforms for continuous parasite propagation. Despite the high prevalence of the parasite, the only US Food and Drug Administration (FDA)-approved treatment of Cryptosporidium infections is nitazoxanide, which has shown moderate efficacy in immunocompetent patients. More importantly, no effective therapeutic drugs are available for treating severe, potentially life-threatening cryptosporidiosis in immunodeficient patients, young children, and neonatal livestock. Thus, safe, inexpensive, and efficacious drugs are urgently required to reduce the ever-increasing global cryptosporidiosis burden especially in low-resource countries. Several compounds have been tested for both in vitro and in vivo efficacy against the disease. However, to date, only a few experimental compounds have been subjected to clinical trials in natural hosts, and among those none have proven efficacious. This review provides an overview of the past and present anti-Cryptosporidium pharmacotherapy in humans and agricultural animals. Herein, we also highlight the progress made in the field over the last few years and discuss the different strategies employed for discovery and development of effective prospective treatments for cryptosporidiosis.

Cyclodextrins: Emerging Medicines of the New Millennium

Cyclodextrins, since their discovery in the late 19th century, were mainly regarded as excipients. Nevertheless, developments in cyclodextrin research have shown that some of these hosts can capture and include biomolecules, highlighting fatty acids and cholesterol, which implies that they are not inert and that their action may be used in specific medicinal purposes. The present review, centered on literature reports from the year 2000 until the present day, presents a comprehensive description of the known biological activities of cyclodextrins and their implications for medicinal applications. The paper is divided into two main sections, one devoted to the properties and applications of cyclodextrins as active pharmaceutical ingredients in a variety of pathologies, from infectious ailments to cardiovascular dysfunctions and metabolic diseases. The second section is dedicated to the use of cyclodextrins in a range of biomedical technologies.

Massive Cryptosporidium infections and chronic diarrhea in HIV-negative patients

Protozoa of the genus Cryptosporidium are common parasites of domestic and wild animals—mammals, birds, reptiles, and fishes. The invasive forms are thick-walled oocysts, which can be present in water supplies, on fruits, vegetables, or in the soil contaminated with feces. In this work, we describe three cases of middle-aged persons with massive Cryptosporidium hominis infection and chronic diarrhea with no immunological abnormalities and no history of previous travels to tropical countries. The lesions discovered during colonoscopy within the large intestine–cryptitis and the histopathological changes were related to massive cryptosporidiosis. All these statements indicate necessity of parasitological stool examination in cases with chronic diarrhea in which no etiological agents are detected, but not only in HIV positive individuals. Parasite’s eradication leads to symptom disappearance as well as improvement of histopathological mucosa alterations.

In vitro evaluation of the suppressive effect of chitosan/poly(vinyl alcohol) microspheres on attachment of C. parvum to enterocytic cells

We present a new strategy to suppress the attachment of Cryptosporidium parvum to the enterocytes cell surface by bioadhesive microspheres. An optimized microsphere system based on chitosan/poly(vinyl alcohol) was prepared by experimental design for the delivery of Diloxanide Furoate-cyclodextrin complex. Formulations were characterized in terms of size, surface charge, drug release, IR spectroscopy and morphology. Bioadhesion properties of chitosan/poly(vinyl alcohol) microspheres, evaluated in the human enterocytic HCT-8 model, were concentration and time dependent. In vitro efficacy of chitosan/poly(vinyl alcohol) microspheres against Cryptosporidium was tested in infected cultures and stages of parasite were assessed by immunofluorescence. The degree of adherence to cells and the inhibition of infectivity were directly related with the lowest level of cross-linking. The C. parvum attachment to cells surface was efficiently suppressed by a concentration of 100 μg/ml of microspheres. TEM observations showed no epithelial-cell damage when microspheres were co-incubated in infected cultures. These results were coincident with the lack of toxicity in cytocompatibility studies. Microspheres remained adhered after 72 h to the apical area of enterocytes. The results suggest that chitosan/poly(vinyl alcohol) with adequate size and appropriate surface characteristics suppress by impairment the attachment of sporozoites to enterocytes and may have a great potential in the oral chemotherapy of Cryptosporidium infections.

Cryptosporidiosis in small ruminants

Cryptosporidiosis is an infection caused by protozoan parasites belonging to the genus Cryptosporidium which is responsible for a potentially severe disease in new-born ruminants. This infection is highly prevalent in small ruminants throughout the world, especially in pre-weaned animals. The clinical expression is different between goat kids and lambs, the infection being generally more severe in the former. Molecular data demonstrate geographical variations in the species of Cryptosporidium infecting small ruminants. They also support the possibility of transmission of zoonotic species from these hosts to humans. Studies are still needed on molecular epidemiology, especially in goats, and on ways to control infection.

Cryptosporidium and Giardia associated with reduced lamb carcase productivity

On two extensive sheep farms in southern Western Australia, 111 (Farm A) and 124 (Farm B) female crossbred lambs (2-6 weeks old) were randomly selected and individually identified using ear tags (a numbered tag and radio-frequency tag) at marking. On five separate occasions, faecal samples were collected and live weight, body condition score (BCS), faecal consistency score (FCS), breech fleece faecal soiling score and faecal dry matter percentage (DM%) were recorded. Lamb hot carcase weight (HCW) and dressing percentage were measured at slaughter. Faecal samples were screened by PCR for Cryptosporidium (18S rRNA, actin and 60 kDa glycoprotein [gp60] loci), Giardia duodenalis (glutamate dehydrogenase [gdh] and triosephosphate isomerise [tpi]) and Campylobacter jejuni (16S rRNA). Observation of Eimeria oocysts and faecal worm egg counts (WECs) were performed using a modified McMaster technique. The WECs were adjusted for FCS for analyses. Faecal samples were screened for patent strongylid infections using PCR (specifically ITS-2 nuclear ribosomal DNA for Teladorsagia circumcincta, Trichostrongylus spp. and Haemonchus contortus). Lambs positive for Cryptosporidium at least once had lighter HCWs by 1.25 kg (6.6%) (P=0.029) and 1.46 kg (9.7%) (P<0.001) compared to lambs never positive for Cryptosporidium for Farms A and B respectively. Similarly, dressing percentages were 1.7% (P=0.022) and 1.9% (P<0.001) lower in Cryptosporidium-positive lambs on Farms A and B respectively. Lambs positive for Giardia at least once had 0.69 kg (P<0.001) lighter HCWs and 1.7% (P<0.001) lower dressing percentages compared to lambs never positive for Giardia on Farm B only. Cryptosporidium-positive lambs at the second sampling were 4.72 (P=0.010) and 3.84 (P=0.002) times more likely to have non-pelleted faeces compared to Cryptosporidium-negative lambs for Farms A and B respectively. Breech fleece faecal soiling scores of Cryptosporidium-positive lambs were 3.36 (P=0.026) and 2.96 (P=0.047) times more likely to be moderate to severe (scores 3-5), compared to negative lambs at the second sampling for Farms A and B respectively. Live weight, growth rate and BCS were inconsistently associated with protozoa detection across different samplings and farms. Adjusted WEC was correlated positively with FCS and negatively with faecal DM%, differing between sampling occasions and farms. Campylobacter jejuni prevalence was very low (<1%). Adjusted WEC were not correlated with carcase attributes, growth rates or live weights. This study is the first to quantify productivity consequences of naturally acquired protozoa infections in lambs managed under extensive farming conditions.

Cryptosporidium and cryptosporidiosis

Cryptosporidium is one of the most common enteric protozoan parasites of vertebrates with a wide host range that includes humans and domestic animals. It is a significant cause of diarrhoeal disease and an ubiquitous contaminant of water which serves as an excellent vehicle for transmission. A better understanding of the development and life cycle of Cryptosporidium, and new insights into its phylogenetic relationships, have illustrated the need to re-evaluate many aspects of the biology of Cryptosporidium. This has been reinforced by information obtained from the recent successful Cryptosporidium genome sequencing project, which has emphasised the uniqueness of this organism in terms of its parasite life style and evolutionary biology. This chapter provides an up to date review of the biology, biochemistry and host parasite relationships of Cryptosporidium.

Activity of an anti-inflammatory drug against cryptosporidiosis in neonatal lambs

The efficacy of the anti-inflammatory drug Bobel-24 against experimental infection by Cryptosporidium parvum was evaluated in neonatal lambs. The animals were treated by oral administration of the drug at 50 or 500 mg/kg of body weight. The prophylactic/therapeutic treatment was started 4 h before inoculation of the lambs with oocysts and was continued for eight consecutive days. The therapeutic treatment was initiated at the onset of diarrhoea, after confirmation of infection, and was continued for six consecutive days. Infection was monitored by daily examination of faecal samples from the first day until 30 days post-inoculation. The criteria considered in evaluating development of the infection and the drug activity were: oocyst shedding, presence of diarrhoea and weight gain at 15 and 30 days post-inoculation. Bobel-24 was effective as a prophylactic/therapeutic treatment at the lowest dose (50 mg/kg of body weight); in the group treated with this dose of drug there was a longer prepatent period, a shorter patent period and a lower intensity of oocyst excretion than in the untreated control group, and the differences were all statistically significant (P < 0.05). Moreover, one animal did not excrete oocysts, and two lambs had diarrhoea, for only 1 and 2 days. In the group treated with the higher dose of the drug, the diarrhoea lasted for a significantly shorter period (P < 0.05) than in the untreated group.

Evaluation of two commercial disinfectants on the viability and infectivity of Cryptosporidium parvum oocysts

Cryptosporidiosis is mainly a problem in neonatal ruminants. Not only do Cryptosporidium spp. spread ubiquitously in our environment, but the protozoa are highly resistant to harsh environmental conditions and disinfectants, and a control measure is urgently required. This study investigated the potential biocidal activity on Cryptosporidium parvum oocysts of two commercial disinfectants developed originally to be used in farms and food-processing industries. The products, containing formaldehyde and hydrogen peroxide respectively, both had some anticryptosporidial effects. The viability and infectivity of purified C. parvum oocysts exposed to both disinfectants at different concentrations and exposure times were evaluated by inclusion or exclusion of vital dye (propidium iodide), use of an excystation technique and infection of suckling mice. Viability assays showed a decrease in oocyst viability associated with an increase in exposure time for each of the concentrations used. The intensity of infection in neonatal mice was significantly lower (P<0.05) than in the control litters.

Cryptosporidiosis in children

Cryptosporidiosis is an important enteric parasitic infection that is associated with significant morbidity and mortality, especially among individuals who are immunosuppressed and infants and children in the developing world. The seroprevalence of this pathogen is high worldwide, suggesting that exposure occurs commonly. The routes of Cryptosporidium spp. transmission are waterborne, food-borne, and occasionally person-to-person. Infected patients can be asymptomatic or develop watery diarrhea and associated enteric symptoms, which are self-limited in immunocompetent persons. In contrast, immunodeficient individuals develop severe, chronic diarrhea that rarely can lead to extra intestinal cryptosporidiosis. Although the diagnosis of Cryptosporidium infection can be established by examining a modified acid-fast stain of stool for the presence of oocysts, enzyme-linked immunoassays are now the diagnostic modalities of choice. Recent clinical trials in pediatric cryptosporidiosis have shown nitazoxanide to be effective therapy.

Efficacy of alpha-cyclodextrin against experimental cryptosporidiosis in neonatal goats

The efficacy of orally administered tablets containing alpha-cyclodextrin, an excipient used in the pharmaceutical industry with demonstrated anticryptosporidial activity in vitro and in neonatal mice, was evaluated in neonatal goat kids. The formulation was evaluated for hardness and was subjected to in vitro drug release studies. Twenty goat kids were orally inoculated with 10(6) oocysts of C. parvum within the first 6 days of age. Half of the animals were treated by oral administration of four tablets of alpha-cyclodextrin/day (500 mg/kg of body weight) for six consecutive days, the treatment beginning on the day of inoculation. Infection was monitored by daily examination of faecal samples from the first day to 25 days post-inoculation. The criteria studied in evaluating efficacy were: oocyst shedding, presence of diarrhoea and weight gain at 15 and 25 days post-inoculation. alpha-cyclodextrin was effective when given at the beginning of infection: there was a longer pre-patent period, a reduction in the patent period and a decrease in the intensity of infection, these differences being statistically significant (P < 0.05) compared with untreated neonatal kids. Moreover, except in one animal, the diarrhoea was prevented in infected neonatal kids. Animals from both groups increased the body weight and no significant differences were seen between the two groups.

In vitro and in vivo efficacy of alpha-cyclodextrin for treatment of experimental cryptosporidiosis

The efficacy of alpha-cyclodextrin against infection by Cryptosporidium parvum was evaluated using in vitro and in vivo models. Cyclodextrins are water-soluble cyclic hexamers of glucose units with hydrophobic cavities capable of solubilizing lipophiles and are widely used as drug excipients in the pharmaceutical industry. The viability of purified C. parvum oocysts, exposed for 30, 60, 90, 120 min and 24h to different concentrations of alpha-cyclodextrin (2.5, 5, 7.5, 10, 12.5 and 15%), was evaluated by inclusion or exclusion of two fluorogenic vital dyes and by an excystation technique. Preventive and curative efficacies against cryptosporidial infections, at different doses (2.5 and 5%) and regimes of administration of alpha-cyclodextrin, were determined in an experimental neonatal mice model. Results of the viability assay showed a decrease in oocyst viability that was associated with an increase in exposure time, for each of the concentrations used. Moreover, a high proportion of nonviable oocysts (81%) was observed when C. parvum oocysts were exposed to alpha-cyclodextrin (2.5%) for 24h. The intensity of infection, determined 7 days post-inoculation by examination of intestinal homogenates, was significantly lower (P<0.05) than in the control litters, for all the assays carried out with alpha-cyclodextrin. Only 38.8% of the animals became infected when the alpha-cyclodextrin solution (5%) was administered 2h before inoculated oocysts, and every 24h at 1 and 2 days post-inoculation.

Formulation and biopharmaceutical issues in the development of drug delivery systems for antiparasitic drugs

The development of really new antiparasitic drugs to market level is a very rare event. A large number of lead structures have already been screened and discarded, the market is large but poor, and the administrative barriers are increasingly high and costly. Novel antiparasitics must not only be better, they must also be substantially safer than the existing repertoire. There are two major aspects to drug development. One is the strategy of pathogen-specific biochemical intervention, the other the strategy of optimal formulation and application. This review focuses on the latter. In finding and adapting innovative and "intelligent", i.e. parasite- and disease-specific formulations and delivery systems, established but deficient drugs might be optimised, enhancing their efficiency and reducing negative side effects at relatively low cost. Further, many promising new ideas are severely hampered by the low water solubility of the antiparasitic drug. Here as well, some of the innovative drug formulation and delivery systems discussed below might offer highly efficient, while technologically simple, solutions.

Controlling the onset of natural cryptosporidiosis in calves with paromomycin sulphate

A prospective, controlled-blind field trial was conducted to evaluate the efficacy and safety of paromomycin sulphate, given for 10 days from birth, in preventing natural cryptosporidiosis in calves. In the untreated control group, oocyst shedding and diarrhoea followed the pattern that had occurred on the farm before the trial, consistent with a perinatal infection, whereas in the treated group, the prepatent period was significantly longer than in the control group (P < 0.01) and oocyst shedding and diarrhoea started only after the drug was withdrawn. However, the regimen did not reduce the incidence of disease in the treated group.

Cryptosporidiosis

PURPOSE OF REVIEW

Cryptosporidiosis is a self-limited diarrheal disease that occurs in the community setting but can be chronic and potentially serious in immunocompromised patients. Community outbreaks are often associated with water-borne transmission. Cryptosporidium research has increased dramatically since the human disease was first recognized in 1976. The present review summarizes recent work in three of the several areas of active Cryptosporidium investigation.

RECENT FINDINGS

Molecular techniques have revealed that current taxonomic designations need re-evaluation and that humans are host to several Cryptosporidium spp. that were once believed to be limited to the veterinary realm. These findings have important public health implications for water quality standards in the USA and other developed countries. Second, techniques for detecting the parasite in infected individuals (or environmental samples) have progressed from acid-fast staining of fecal smears to the currently used antibody-based systems (enzyme immunoassays and immunofluorescent assays). New molecular methodologies, based on polymerase chain reaction amplification of gene loci, are being developed to improve the sensitivity and specificity for diagnostic and epidemiologic purposes. Third, curative therapy is attained only by an effective immune response or the reconstitution of a failing immune system in the compromised host. However, several drugs are in development, and compounds such as nitazoxanide appear to hold some promise.

SUMMARY

Cryptosporidiosis continues to be a serious problem in immunocompromised patients and on a worldwide scale in undernourished infants and children. The lack of an effective treatment, and the propensity of the parasite to survive in and be transmitted through source waters make this an important public health threat.

Recent advances in the search for new anti-coccidial drugs

Coccidia provide a rich hunting ground for drug-designers, as there are significant biochemical differences between the parasites and their hosts. Recent years have brought the discovery of the plastid and its possible metabolic machinery, characterisation of acidocalcisomes, reports on the apparent absence from some coccidia of a typical mitochondrion, and the discovery of the mannitol cycle and shikimate pathway in the parasites. Moreover, modern technologies such as genomics and proteomics are bringing new insights into the biochemistry of coccidia and highlighting possible drug targets in abundance. A major issue for would-be drug discoverers is to decide upon the targets to prioritise. This review provides an update on recent findings on how coccidia differ biochemically from vertebrates. It includes discoveries within coccidian parasites themselves but also uses findings in Plasmodium to provide an overview of biochemical features that may be characteristics of many apicomplexan parasites and so potential targets for broad-spectrum drugs.

Companion animal parasitology: a clinical perspective

In recent years there have been many changes to the ways that clinical veterinary science is conducted and nowhere is this more evident than in companion animal practice. Veterinarians working with pet dogs and cats are facing new challenges associated with the emergence and re-emergence of parasitic diseases. Some, such as Neospora caninum, have been recently recognised; others like Giardia and Cryptosporidium have been reported with increasing frequency, in part as a result of laboratory tests with improved sensitivity and specificity. In many regions, the emergence of parasitic diseases has been a consequence of pet travel and exotic diseases pose a unique diagnostic challenge for the veterinarian, as the index of suspicion for these conditions may be absent. The ranges of certain vector-borne diseases such as babesiosis, hepatozoonosis, ehrlichiosis, leishmaniasis and dirofilariasis are extending due to ecological and climatic changes and enhanced by animals with subclinical infection returning home from endemic areas. In companion animal practice, veterinarians have the additional responsibility of providing accurate information about the zoonotic transmission of parasite infections from pets, especially to those most vulnerable such as children, the elderly and the immunocompromised. Effective education is vital to allay public concerns and promote responsible pet ownership.