BACKGROUND: The bovine lungworm Dictyocaulus viviparus negatively impacts bovine health and leads to substantial economic losses. Lungworm infections can be difficult to manage due to the unpredictable and severe nature of clinical outbreaks. Despite the widespread use of macrocyclic lactones (MLs) in grazing cattle in the UK, there have been no confirmed reports of resistant lungworms to date, with only one case of anthelmintic-resistant (ML) lungworm confirmed worldwide.
METHODS: Lungworm Baermann filtrations were conducted on first-season grazing dairy calves as part of a wider study investigating anthelmintic resistance in gastrointestinal nematodes in Scotland using the faecal egg count reduction test.
RESULTS: Clinical signs and significant numbers of lungworm larvae in faeces were observed after treatment with either ivermectin or moxidectin.
CONCLUSIONS: There are no established guidelines for the diagnosis of resistant lungworms in the field. Currently, resistance can only be diagnosed after a controlled efficacy test has been conducted. This limits the conclusions that can be drawn; however, they are highly suggestive of resistance.
CONCLUSIONS: This short report describes the inefficacy of ivermectin and moxidectin against D. viviparus and is highly suggestive of ML resistance.

Lungworm infection, or verminous pneumonia, is a parasitic disease that causes serious problems in small and large ruminants. Despite the fact that nematodes of the genus Dictyocaulus in cattle and sheep are the main cause of this disease, there are few studies on the natural infections of South American camelids. For this reason, this study aims to report the natural infection by Dictyocaulus filaria in vicunas (Vicugna vicugna) for the first time. During a shearing season (chaku) in Cuzco, Peru, two accidentally killed adult vicunas were submitted to the IVITA-Marangani research center in Cuzco for their respective necropsies. The tracheas of both vicunas had numerous nematodes, as seen during the necropsy. The nematodes were collected in 70% ethanol and were morphologically identified as D. filaria. Likewise, the DNA of six nematodes was extracted, and the ITS2 region and the 28S rRNA gene were amplified and sequenced. The nucleotide sequences of both genetic markers were up to 100% identical with previously reported D. filaria DNA sequences found in the goat yearlings from Turkey, sheep from Iran, Turkey, and India, and the argali from Uzbekistan, which confirmed the morphological diagnosis. This finding represents the first molecular confirmation of a natural D. filaria infection in a South American camelid. It will be necessary to carry out future studies to know the current situation of verminous pneumonia in domestic and wild South American camelids and to know the negative effects of the disease on them.

Whilst healthy adult farmed red deer show little clinical indication of parasite infection, they may still be maintaining infection levels on the farm through low-level shedding of nematode eggs and lungworm larvae. This work was undertaken to establish the long-term distribution of parasite counts, to determine whether the higher counts seen in previous trials are repeatable across the same animals. All adult female red deer on a New Zealand North Island property were faecal sampled (n = 209), weighed, and body condition scored (BCS) on five sampling occasions from March - August 2021. Faecal samples were processed by modified Baermanns to recover, identify, and enumerate lungworm 1st stage larvae (FLC), and nematode faecal egg counts (FEC) were determined by mini-FLOTAC. Between animal variation for FEC was significant (p < 0.001); whilst many counts were low to zero, a few individuals were consistently shedding higher egg counts. Younger animals tended to have higher egg counts (p = 0.003), but there was no association between FEC and BCS (p = 0.22), and FEC and liveweight (p = 0.58). Modelling of the data indicated that 50% of the egg output resulted from 21% of the animals. Additionally, there was no significant association between the higher egg counts and the gastrointestinal nematode classification; \'long tails\' (likely Oesophagostomum sp.) p = 0.76, and the Ostertagiinae complex p = 0.75. Lungworm counts tended to be very low (0 - 26 lpg); consistent with previous trials and literature in farmed adult deer. However, between animal differences were statistically significant (p < 0.001) indicating some animals were passing more larvae than others, and poorer conditioned animals (BCS 2.5) were significantly associated with higher larval count (p = 0.03). There was no relationship between larval count and age (p = 0.62) and larval count and liveweight (p = 0.22). Modelling indicates that 50% of pasture larval contamination was contributed by 15% of the animals. There was no correlation between nematode egg count and lungworm larvae count (p = 0.22). Adult deer may play an important role as a source of infection for young deer, therefore, an improved understanding of the distribution of infection is needed to improve parasite control.

暂无摘要。

Lungworms of the genus Dictyocaulus are causative agents of parasitic bronchitis in domestic and wild ungulates. This study investigates the distribution, morphology and genetic diversity of D. cervi and a new lungworm species, Dictyocaulus skrjabini n. sp. infecting red deer Cervus elaphus, fallow deer Dama dama and moose Alces alces in Poland and Sweden. The study was conducted on 167 red deer from Poland and on the DNA of lungworms derived from 7 fallow deer, 4 red deer and 2 moose collected in Sweden. The prevalence of D. cervi and D. skrjabini n. sp. in dissected red deer in Poland was 31.1% and 7.2%, respectively. Moreover, D. skrjabini n. sp. was confirmed molecularly in 7 isolates of fallow deer lungworms and 1 isolate of red deer lungworms from Sweden. Dictyocaulus skrjabini n. sp. was established based on combination of their distinct molecular and morphological features; these included the length of cephalic vesicle, buccal capsule (BC), buccal capsule wall (BCW), distance from anterior extremity to the nerve ring, the width of head, oesophagus, cephalic vesicle, BC and BCW, as well as the dimensions of reproductive organs of male and female. Additionally, molecular analyses revealed 0.9% nucleotide sequence divergence for 1,605 bp SSU rDNA, and 16.5–17.3% nucleotide sequence divergence for 642 bp mitochondrial cytB between D. skrjabini n. sp. and D. cervi, respectively, and 18.7–19% between D. skrjabini n. sp. and D. eckerti, which translates into 18.2–18.7% amino acid sequence divergence between D. skrjabini n. sp. and both lungworms.

Dictyocaulus xanthopygus sp. nov. (Nematoda: Trichostrongyloidea) was isolated from the lungs of the Manchurian wapiti in Primorsky kray, Russia. The newly described species exhibits morphological characteristics of Dictyocaulus but is distinct from congeneric species based on morphological (lengths of body and esophagus, distances from the anterior end to nerve ring and to excretory pore, the thickness of the buccal capsule, etc.) and molecular features. High levels of genetic divergence as well as Bayesian phylogenetic analyses based on 18S rRNA nuclear and cox1 mitochondrial genes supported the independence of Dictyocaulus xanthopygus sp. nov. Secondary structures of helix 39 of 18S rRNA were identical, while ES9 adjacent to the helix has a unique conformation for newly described worms. Energy-efficient conformational rearrangements of rRNA secondary structures can be applicable in studies on the pathogenesis, epidemiology, taxonomy and evolutionary biology of parasites. Additionally, bracketed dichotomous keys to six valid species of Dictyocaulus were prepared.

暂无摘要。

Nematodes of the genus Dictyocaulus are the causative agents of parasitic bronchitis and pneumonia in several domestic and wild ungulates. Various species have been described in wild cervids, as the case of Dictyocaulus cervi in red deer, recently described as a separate species from Dictyocaulus eckerti. In Italy, information on dictyocaulosis in wildlife is limited and often outdated. In this work, 250 red deer were examined for the presence of Dictyocaulus spp. in two areas of the Italian Alps (n = 104 from Valle d\'Aosta, n = 146 from Stelvio National Park), and the retrieved lungworms were molecularly characterized. Lungworms were identified in 23 and 32 animals from Valle d\'Aosta and Stelvio National Park, respectively. The nematodes, morphologically identified as D. cervi, were characterized molecularly (18S rDNA, ITS2, and coxI). Consistently, almost all specimens were found to be phylogenetically related to D. cervi. Three individuals, detected from both study sites and assigned to an undescribed Dictyocaulus sp., clustered with Dictyocaulus specimens isolated from red deer and fallow deer in previous studies. Within each of D. cervi and the undescribed Dictyocaulus sp., the newly isolated nematodes phylogenetically clustered based on their geographical origin. This study revealed the presence of D. cervi in Italian red deer, and an undetermined Dictyocaulus sp. that should be more deeply investigated. The results suggest that further analyses should be focused on population genetics of cervids and their lungworms to assess how they evolved, or co-evolved, throughout time and space and to assess the potential of transmission towards farmed animals.

The lungworm Dictyocaulus viviparus has an important role in cattle health and productivity worldwide, since infections can lead to substantial economic losses. Despite its importance, few studies investigating the epidemiological aspects of infection by this parasite have been conducted. The aim of this study was to report the occurrence of lungworm infection in beef cattle herds reared in an area of livestock production in the northeastern region of Brazil. From September 2020 to August 2021, monthly fecal samples (n = 493) were collected from 46 beef cattle. Among all the animals assessed, lungworm larvae were detected in 8.7% (4/46). None of them presented any clinical sign suggestive of infection by lungworm parasites. Twenty larvae were retrieved, with the minimum number (n = 1) detected in October and December, and the maximum number (n = 13) in November. These presented a mean length of 363 μm (± 28.65 μm) and mean width of 19 μm (± 1.03 μm), and were morphologically similar to Dictyocaulus sp.. This study reports the occurrence of this parasite in this livestock production area. Lastly, local veterinarians need to be aware of inclusion of this parasite in the differential diagnosis of other respiratory infections in beef cattle.

Outbreaks of cattle lungworm disease (Dictyocaulus viviparus) are explosive and costly. The unpredictability of the disease often encourages farmers to apply blanket anthelmintic treatments to the herd, which impede the acquisition of immunity, increase the risk of drug resistance, and interfere with efforts to reduce anthelmintic use against ubiquitous gastrointestinal nematodes. Improving our understanding of the factors which lead to a high risk of infection with lungworm, (including climatic pressure), would support a more targeted management. We present GLOWORM-FL-DV, the first mathematical model of the free-living stages of D. viviparus. The ecology of D. viviparus is unique compared with other strongylid nematodes due to its relationship with Pilobilus spp. fungi, which enhance the transmission potential. The role of the fungi was therefore incorporated into the model framework, informed by laboratory observations of Pilobolus spp. development and sporulation. The thermal niche of D. viviparus was characterised based on published and laboratory observations. Mortality of parasitic larvae increased significantly below 0oC, and larval development occurred above 1.4oC, whereas the estimated minimum temperature for migration via Pilobolus spp. was 8.8oC. Model predictions were compared with antibody levels in bulk milk tank samples collected at two-weekly intervals from eight dairy herds across Great Britain over two grazing seasons. The model predicted high levels of larval abundance on pasture 46 days (38-52 days) before a rise in antibody levels and 22-26 days before the onset of clinical signs. The model assesses the impact of climate and weather on lungworm larval availability at pasture and provides a framework for the development of a risk forecasting system. This could help to focus vigilance for clinical signs at high-risk times and facilitate the targeted use of anthelmintics to prevent outbreaks, in support of sustainable parasite control.