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Gastrointestinal Tract
Published in Pritam S. Sahota, James A. Popp, Jerry F. Hardisty, Chirukandath Gopinath, Page R. Bouchard, Toxicologic Pathology, 2018
Judit E. Markovits, Graham R. Betton, Donald N. McMartin, Theresa Boulineau
Infections or infestations may occur in nonhuman primates, especially in studies with immunosuppressive agents, although the ciliate protozoa, Balantidium spp., may be seen in the large intestinal lumen in immunocompetent nonhuman primates or dogs. Invasive balantidiasis (associated with mucosal damage and the presence of organisms extending into the submucosa) or flask-shaped ulcers due to Entamoeba histolytica may occur in immunosuppressed nonhuman primates. In the small intestine, the most commonly encountered infestation is cryptosporidiosis resulting in villus blunting. The organism is recognized as 1–4 μm round structures. Giardia appearing as racquet-shaped delicate organism adjacent to the epithelium of the proximal small intestine may be present in immunosuppressed nonhuman primates or mice. However, they are easily overlooked because they may appear as mucus droplets in crypts. Viral inclusions and associated mucosal changes are not common in the gut of nonhuman primates dosed with immunosuppressive xenobiotics, which include adenoviral and cytomegaloviral infections. Activation of an LCV in macaques may result in lymphoproliferative changes that involve segments of the intestinal tract and are typically composed of B lymphocytes (Figure 11.22a–d). Other organisms in nonhuman primates encountered include Spironucleus, a delicate flagellate organism in the large intestine. Nodular worms (Oesophagostomum sp.) were seen most frequently spontaneously in nonhuman primates (the nodules being composed of a granulomatous reaction associated with the intralesion parasite), whereas whip worms (Trichuris sp.) were encountered less frequently and mostly in immunosuppressed animals. Nematodes are seldom seen in rodents due to modern animal husbandry, but occasionally, pinworms (Syphacia muris or Aspicularis tetraptera) may be encountered in rats (Elwell and McConnell 1990). Bacterial infections that are commonly seen in outdoor-housed macaques (campylobacteriosis and shigellosis) are uncommon in animals on toxicity studies. In addition to nonhuman primates, Campylobacter jejuni may be encountered as an etiology of acute enteric inflammation in dogs. Yersiniosis is another bacterial infection that occurs primarily in outdoor-housed macaques in wet, colder months, but this etiology, as others, may also be seen indoors in a quarantine setting. Yersiniosis is characterized by large flower petal-like bacterial colonies surrounded by neutrophils. During testing of antibiotics, the toxicologic pathologist may encounter pseudomembranous colitis characterized by a necrotizing colitis containing small mucosal deficits being covered by a “volcanic eruption” of exudates composed of neutrophils and fibrin (Lowenstein 2003). New World monkeys (especially callitrichids) are not commonly used as toxicologic species, but the practicing toxicologic pathologist needs to be aware of the widespread chronic colitis present in many colonies that may be part of the marmoset wasting disease (Lowenstein 2003; Chalmers et al. 1983). The lesion varies in morphology from a primarily mononuclear infiltrate to mucosal deficits along with neutrophilic infiltrate and crypt abscesses.
Helminths, hosts, and their microbiota: new avenues for managing gastrointestinal helminthiases in ruminants
Published in Expert Review of Anti-infective Therapy, 2020
Alba Cortés, James Rooney, Dave J. Bartley, Alasdair J. Nisbet, Cinzia Cantacessi
In sheep, economic losses from helminthiases are mainly attributable to gastrointestinal nematode species (GIN; cf. Table 1), and in particular to parasites residing in the abomasum (Table 1) (i.e. Haemonchus contortus, Teladorsagia (Tel.) circumcincta and Trichostrongylus (T.) axei), and in the small intestine (i.e. T. colubriformis and T. vitrinus). Other GIN impacting production in small ruminants (cf. Table 1) are Nematodirus spp., Cooperia spp. and the large intestinal nematodes Chabertia ovina and Oesophagostomum spp. In cattle, the main species causing economic impact reside in the abomasum (Ostertagia ostertagi and Haemonchus placei) and in the small intestine (Cooperia punctata and C. oncophora). In agricultural settings, hosts are usually simultaneously infected by multiple species of GIN, and infections are controlled using a mixture of pasture management and broad-spectrum anthelmintic compounds (cf. Table 1). Nevertheless, drug resistance to all available classes of anthelmintics is widespread [1,2] and, coupled with the slow development of new antiparasitics as well as the limitations in drug use in organic farms, makes the search for alternative strategies for infection and disease control a top priority. Vaccines (cf. Table 1) have the potential to offset some of the issues linked to anthelmintic use, and are a potentially highly effective tool for control of helminth infections in ruminants; nevertheless, vaccines are unlikely to provide sufficient protection to entirely replace any other strategy of parasite control in livestock. Since the 1950s, significant research efforts have been channeled into the discovery of vaccines against parasitic nematodes in ruminants [3], with several promising prototypes being developed (e.g. [4]). However, during this time, only two vaccines to control helminths of ruminants have reached commercialization, i.e. Dictol (currently Bovilis Huskvac™, MSD Animal Health) for protection of cattle against lungworm (Dictyocaulus viviparus) and Barbervax® for protection of sheep against the barber’s pole worm (H. contortus) [5]. This relatively poor return on research investment in the area is largely due to inherent difficulties linked to designing effective vaccines against complex metazoan organisms, which are able to exist and thrive inside the host by evading and modulating the host-immune function [6].