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The Future of Parasitology
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
Improvement of mathematical models is needed to better predict (1) spatial and temporal fluctuations in parasites abundance, including those resulting from drug control, and (2) the impact of drug resistance. Modeling efforts indicate that rotation of drug treatments has more of an impact on controlling sheep nematodes (Trichostrongylus colubriformis, Haemonchus contortus and Teladorsagia (Ostertagia) circumcincta) and preventing the emergence of drug resistance than does the use of refugia that leave up to 10% of adult sheep untreated. In addition, the simultaneous deployment of combinations of old and new drugs was more effective than the rotation of drugs.
Phytochemicals from Wild Medicinal and Aromatic Plants of Argentina
Published in Mahendra Rai, Shandesh Bhattarai, Chistiane M. Feitosa, Wild Plants, 2020
María Paula Zunino, Andrés Ponce, Alejandra Omarini, Julio Alberto Zygadlo
The parasitic infection of Haemonchus contortus, an endoparasitic nematode, was related to the death of sheep. On the other hand, endoparasitic diseases result in economic losses linked to use of anthelmintic drugs. An aqueous extract of Senecio brasiliensis (Spreng.) Less. displayed ovicidal activity against H. contortus, but its larvicidal property was less pronounced (Soares et al. 2019). Thus, the egg hatching inhibition was associated with high concentration of integerrimine (a macrolide alkaloid) from leaves extract of S. brasiliensis. (Soares et al. 2019). Among liver diseases, the hepatic sinusoidal obstructive syndrome is mainly linked in rural areas with ingestion of pyrrolidine alkaloid, present in S. brasiliensis. The treatment of menopause by drinking Senecio tea daily is another cause of the disease (Barcelos et al. 2019). These poisoning products of the alkaloids are frequent with the consumption of Senecio as a medicinal plant, although in the ethnobotany studies, the use of this plant in different communities was mentioned (Bolzan et al. 2007).
The Link Between Immune Responses And Behaviour In Sheep
Published in Husband Alan J., Behaviour and Immunity, 2019
G.R. Gates, L.R. Fell, J.J. Lynch, D.B. Adams, J.P. Barnett, G.N. Hinch, R.K. Munro, H.I. Davies
The Haemonchus contortus larvae used in the experiments reported here were obtained from cultures of faeces of sheep harbouring a pure infection. Faecal egg counts were made by the McMaster method14 on samples collected directly from the rectum.
Identifying novel candidates and configurations for human helminth vaccines
Published in Expert Review of Vaccines, 2021
Efforts to generate vaccines against helminths date back 50 years to the development of a dog hookworm vaccine using irradiated infective larvae of Ancylostoma caninum [9,10]. While not a commercial success (as the vaccine did not entirely prevent transmission), this demonstrated that vaccine-induced immunity was possible, and paved the way for a similar irradiated larval vaccine (Huskvac) for lungworm (Dictyocaulus viviparus) in cattle [11]. A separate initiative, also in the veterinary arena, led to the development of a vaccine based on purified intestinal antigens of Haemonchus contortus (the ‘Barber’s Pole’ worm), now marketed as Barbervax [12,13]. Finally, successful recombinant vaccines have been pioneered against cestode tapeworms of livestock [14], now marketed in a number of tropical countries as CysVax (for Taenia solium in pigs) and Hidatil (for Echinococcus granulosus in ruminants).
Moxidectin: an oral treatment for human onchocerciasis
Published in Expert Review of Anti-infective Therapy, 2020
Philip Milton, Jonathan I. D. Hamley, Martin Walker, María-Gloria Basáñez
Resistance to moxidectin (and to ivermectin) is common in parasitic nematodes of livestock and companion animals [67]. Even in resistant populations, moxidectin retains a higher efficacy than the avermectins, but continued exposure can result in therapeutic failure and cross-resistance between moxidectin and ivermectin [67]. The genetic analysis of O. volvulus taken from poor and good responders in Ghana and Cameroon found that decreased ivermectin efficacy in human onchocerciasis may be determined by (geographically different) quantitative trait loci, mostly unrelated to the few candidate genes and mechanisms that had been proposed in resistance studies of veterinary parasitic nematodes [66]. In Haemonchus contortus, a major quantitative trait locus has been established to be associated with ivermectin resistance [68], suggesting that the mechanisms of ivermectin resistance in parasites of humans and farmed ruminants may be somewhat distinct. However, if moxidectin were widely adopted for large-scale treatment of onchocerciasis and other endo/ectoparasitic infections of humans, it would be essential to regularly monitor its efficacy, and understand its impact on the genetic diversity and structure of O. volvulus (and other parasite) populations. This is particularly important for onchocerciasis for which the ultimate goal is global elimination (i.e. reducing the potentially rescuing effect that untreated refugia could have on the spread of SORs, but see [69] for a review of the conventional wisdom of, and challenges to the concept of refugia in mitigating anthelmintic resistance).
In vitro inhibition of the hepatic S-oxygenation of the anthelmintic albendazole by the natural monoterpene thymol in sheep
Published in Xenobiotica, 2020
Victoria Miró, Adrian Lifschitz, Paula Viviani, Carolina Rocha, Carlos Lanusse, Livio Costa, Guillermo Virkel
Thymol (TML) (2-isopropyl-5-methylphenol) is a natural monoterpene phenol present in essential oils from plants of the genus Lippia and Thymus (Elandalousi et al., 2013; Gomes et al., 2012). This compound possesses a number of pharmacological effects, including antioxidant, anti-inflammatory, analgesic, anti-hemolytic, antibacterial, antifungal, anti-tumoral, and anti-mutagenic properties among others (Meeran et al., 2017). Therefore, it is currently used as an alternative or complementary pharmacological tool for the treatment of several diseases in human medicine (Meeran et al., 2017). In addition, it has been shown that TML possesses in vitro anthelmintic activity, particularly against ruminant’s nematodes such as Haemonchus contortus eggs, larvae and adult parasites (André et al., 2017; Camurça-Vasconcelos et al., 2007; Elandalousi et al., 2013; Ferreira et al., 2016; Katiki et al., 2017). This finding poses the need for further research on the potential of this phytochemical compound as a pharmacological alternative to treat gastrointestinal parasitic diseases of ruminants.