Could ectoparasites act as vectors for prion diseases?

Mitigation Strategies against Food Safety Contaminant Transmission from Black Soldier Fly Larva Bioconversion

The black soldier fly larva, Hermetia illucens, can efficiently convert organic waste into biomatter for use in animal feed. This circularity comes with a risk of contaminating downstream consumers of the larval products with microbes, heavy metals, and other hazards potentially present in the initial substrate. This review examines research on mitigation techniques to manage these contaminants, from pretreatment of the substrate to post-treatment of the larvae. While much research has been done on such techniques, little of it focused on their effects on food safety contaminants. Cheap and low-technology heat treatment can reduce substrate and larval microbial load. Emptying the larval gut through starvation is understudied but promising. Black soldier fly larvae accumulate certain heavy metals like cadmium, and their ability to process certain hazards is unknown, which is why some government authorities are erring on the side of caution regarding how larval bioconversion can be used within feed production. Different substrates have different risks and some mitigation strategies may affect larval rearing performance and the final products negatively, so different producers will need to choose the right strategy for their system to balance cost-effectiveness with sustainability and safety.

Nasal bots carry relevant titers of CWD prions in naturally infected white-tailed deer

Chronic wasting disease (CWD) is a prion disease affecting farmed and free-ranging cervids. CWD is rapidly expanding across North America and its mechanisms of transmission are not completely understood. Considering that cervids are commonly afflicted by nasal bot flies, we tested the potential of these parasites to transmit CWD. Parasites collected from naturally infected white-tailed deer were evaluated for their prion content using the protein misfolding cyclic amplification (PMCA) technology and bioassays. Here, we describe PMCA seeding activity in nasal bot larvae collected from naturally infected, nonclinical deer. These parasites efficiently infect CWD-susceptible mice in ways suggestive of high infectivity titers. To further mimic environmental transmission, bot larvae homogenates were mixed with soils, and plants were grown on them. We show that both soils and plants exposed to CWD-infected bot homogenates displayed seeding activity by PMCA. This is the first report describing prion infectivity in a naturally occurring deer parasite. Our data also demonstrate that CWD prions contained in nasal bots interact with environmental components and may be relevant for disease transmission.

External ophthalmomyiasis by Oestrus ovis in tourists visiting Italy. Report of three cases and a literature review

BACKGROUND

Oestrus ovis is a dipteran parasite responsible of myiasis in small ruminants and reported as the causative agent of myiasis in humans particularly in sheep farming areas. In recent years, several human cases had been reported without any previous history of exposure to livestock or visit to rural areas.

CASE PRESENTATION

We describe three clustered cases of ophthalmomyiasis externa in tourists in Sardinia and Sicily and discuss them in the light of the published literature. The patients presented ocular irritation, foreign body sensation, pain, redness, and lacrimation of the eyelids. After extraction, all the larvae were morphologically and molecularly confirmed as L1 instar of O. ovis larvae.

CONCLUSIONS

The present study points out the need to draw attention and awareness among the physicians, and to consider ophthalmomyiasis when consulted for conjunctivitis in the summer and spring seasons.

Food Wastes as a Potential new Source for Edible Insect Mass Production for Food and Feed: A review

About one-third of the food produced annually worldwide ends up as waste. A minor part of this waste is used for biofuel and compost production, but most is landfilled, causing environmental damage. Mass production of edible insects for human food and livestock feed seems a sustainable solution to meet demand for animal-based protein, which is expected to increase due to rapid global population growth. The aim of this review was to compile up-to-date information on mass rearing of edible insects for food and feed based on food wastes. The use and the potential role of the fermentation process in edible insect mass production and the potential impact of this rearing process in achieving an environmentally friendly and sustainable food industry was also assessed. Food waste comprises a huge nutrient stock that could be valorized to feed nutritionally flexible edible insects. Artificial diets based on food by-products for black soldier fly, house fly, mealworm, and house cricket mass production have already been tested with promising results. The use of fermentation and fermentation by-products can contribute to this process and future research is proposed towards this direction. Part of the sustainability of the food sector could be based on the valorization of food waste for edible insect mass production. Further research on functional properties of reared edible insects, standardization of edible insects rearing techniques, safety control aspects, and life cycle assessments is needed for an insect-based food industry.

Opportunistic Oral Infections

An opportunistic infection (OI) is a disease of microbial cause or pathogenesis generally thought to occur in hosts with weakened immunity. Oral OIs are associated with many risk factors and pathogens. Causative organisms for oral OIs have unique modes of transmission. The clinical presentation of oral OIs is heterogeneous and diagnosis can be challenging. Therefore, laboratory identification of causative pathogens is useful for definitive diagnosis and targeted therapeutics, and can be achieved by biological, serologic, histologic, and/or molecular methods. Clinical risk assessment and history with review of systems, and accurate diagnosis, treatment, and follow-up, are essential.

Scrapie Agent (Strain 263K) can transmit disease via the oral route after persistence in soil over years

The persistence of infectious biomolecules in soil constitutes a substantial challenge. This holds particularly true with respect to prions, the causative agents of transmissible spongiform encephalopathies (TSEs) such as scrapie, bovine spongiform encephalopathy (BSE), or chronic wasting disease (CWD). Various studies have indicated that prions are able to persist in soil for years without losing their pathogenic activity. Dissemination of prions into the environment can occur from several sources, e.g., infectious placenta or amniotic fluid of sheep. Furthermore, environmental contamination by saliva, excrements or non-sterilized agricultural organic fertilizer is conceivable. Natural transmission of scrapie in the field seems to occur via the alimentary tract in the majority of cases, and scrapie-free sheep flocks can become infected on pastures where outbreaks of scrapie had been observed before. These findings point to a sustained contagion in the environment, and notably the soil. By using outdoor lysimeters, we simulated a contamination of standard soil with hamster-adapted 263K scrapie prions, and analyzed the presence and biological activity of the soil-associated PrP^Sc and infectivity by Western blotting and hamster bioassay, respectively. Our results showed that 263K scrapie agent can persist in soil at least over 29 months. Strikingly, not only the contaminated soil itself retained high levels of infectivity, as evidenced by oral administration to Syrian hamsters, but also feeding of aqueous soil extracts was able to induce disease in the reporter animals. We could also demonstrate that PrP^Sc in soil, extracted after 21 months, provides a catalytically active seed in the protein misfolding cyclic amplification (PMCA) reaction. PMCA opens therefore a perspective for considerably improving the detectability of prions in soil samples from the field.

Fate of prions in soil: detergent extraction of PrP from soils

The transmissible spongiform encephalopathies (TSEs) are caused by infectious agents whose structures have not been fully characterized but include abnormal forms of the host protein PrP, designated PrP(Sc), which are deposited in infected tissues. The transmission routes of scrapie and chronic wasting disease (CWD) seem to include environmental spread in their epidemiology, yet the fate of TSE agents in the environment is poorly understood. There are concerns that, for example, buried carcasses may remain a potential reservoir of infectivity for many years. Experimental determination of the environmental fate requires methods for assessing binding/elution of TSE infectivity, or its surrogate marker PrP(Sc), to and from materials with which it might interact. We report a method using Sarkosyl for the extraction of murine PrP(Sc), and its application to soils containing recombinant ovine PrP (recPrP). Elution properties suggest that PrP binds strongly to one or more soil components. Elution from a clay soil also required proteinase K digestion, suggesting that in the clay soil binding occurs via the N-terminal of PrP to a component that is absent from the sandy soils tested.

Myiasis as a risk factor for prion diseases in humans

Prion diseases are transmissible spongiform encephalopathies of humans and animals. The oral route is clearly associated with some prion diseases, according to the dissemination of bovine spongiform encephalopathy (BSE or mad cow disease) in cattle and kuru in humans. However, other prion diseases such as scrapie (in sheep) and chronic wasting disease (CWD) (in cervids) cannot be explained in this way and are probably more associated with a pattern of horizontal transmission in both domestic and wild animals. The skin and mucous membranes are a potential target for prion infections because keratinocytes and lymphocytes are susceptible to the abnormal infective isoform of the prion protein. Iatrogenic transmission of Creutzfeldt-Jakob disease (CJD) was also recognized after corneal transplants in humans and scrapie was successfully transmitted to mice after ocular instillation of infected brain tissue, confirming that these new routes could also be important in prion infections. Some ectoparasites have been proven to harbour prion rods in laboratory experiments. Prion rods were identified in both fly larvae and pupae; adult flies are also able to express prion proteins. The most common causes of myiasis in cattle and sheep, closely related animals with previous prion infections, are Hypoderma bovis and Oestrus ovis, respectively. Both species of flies present a life cycle very different from human myiasis, as they have a long contact with neurological structures, such as spinal canal and epidural fat, which are potentially rich in prion rods. Ophthalmomyiases in humans is commonly caused by both species of fly larvae worldwide, providing almost direct contact with the central nervous system (CNS). The high expression of the prion protein on the skin and mucosa and the severity of the inflammatory response to the larvae could readily increase the efficiency of transmission of prions in both animals and humans.

Comparative evidence for a link between Peyer's patch development and susceptibility to transmissible spongiform encephalopathies

Background

Epidemiological analyses indicate that the age distribution of natural cases of transmissible spongiform encephalopathies (TSEs) reflect age-related risk of infection, however, the underlying mechanisms remain poorly understood. Using a comparative approach, we tested the hypothesis that, there is a significant correlation between risk of infection for scrapie, bovine spongiform encephalopathy (BSE) and variant CJD (vCJD), and the development of lymphoid tissue in the gut.

Methods

Using anatomical data and estimates of risk of infection in mathematical models (which included results from previously published studies) for sheep, cattle and humans, we calculated the Spearman's rank correlation coefficient, r_s, between available measures of Peyer's patch (PP) development and the estimated risk of infection for an individual of the corresponding age.

Results

There was a significant correlation between the measures of PP development and the estimated risk of TSE infection; the two age-related distributions peaked in the same age groups. This result was obtained for each of the three host species: for sheep, surface area of ileal PP tissue vs risk of infection, r_s = 0.913 (n = 19, P < 0.001), and lymphoid follicle density vs risk of infection, r_s = 0.933 (n = 19, P < 0.001); for cattle, weight of PP tissue vs risk of infection, r_s = 0.693 (n = 94, P < 0.001); and for humans, number of PPs vs risk of infection, r_s = 0.384 (n = 46, P = 0.008). In addition, when changes in exposure associated with BSE-contaminated meat were accounted for, the two age-related patterns for humans remained concordant: r_s = 0.360 (n = 46, P = 0.014).

Conclusion

Our findings suggest that, for sheep, cattle and humans alike there is an association between PP development (or a correlate of PP development) and susceptibility to natural TSE infection. This association may explain changes in susceptibility with host age, and differences in the age-susceptibility relationship between host species.

Risk analysis of ectoparasites acting as vectors for chronic wasting disease

Prion diseases are rare neurodegenerative diseases of humans and animals with a lethal evolution. Animal prion infections, such as chronic wasting disease (CWD) and scrapie (sheep) have shown a pattern of horizontal transmission. CWD is an endemic disease that has been affecting thousands of domestic and wild cervids in US for the last three decades. The mode of contamination is not known, although direct contact between infected and non-infected animals via saliva, urine and feces have been considered. Increasing spread of CWD has raised concerns about the potential transmission to humans and the conversion of human prion protein by CWD-associated prions has been demonstrated in laboratory experiments. Fly larvae exposed to brain infected material were able to readily transmit scrapie to hamsters. Prion rods were identified in both larvae and fly pupae. New lines of evidence confirmed that adult flies are also able to express prion proteins. The most prevalent species of myiasis in cattle, sheep and wild cervids (Hypoderma spp.) present a very different life cycle from human myiasis, with a long contact with neurologic structures, such as the spinal canal and epidural fat, that are potentially rich in prion rods. Considering the huge amount of fly larvae that affects each animal, it is important to discuss the possibility that these ectoparasites could theoretically act as reservoirs and vectors for CWD and other prion diseases. It is critical to recognize all the possible factors involved in CWD transmission since ectoparasites could be handled in an easier way than the environmental persistence of infectious prions.