In this issue:
- WormFaxNSW-August / Outlook from the Outhouse
- ParaBoss News – September 2017 – Feature Articles
- (Immunity loss at lambing and kidding (Kahn) – and – Flystrike Assist app)
- Macracanthorhynchus photos – Jayce Morgan, NSW DPI
- Macracanthorhynchus hirudinaceus in feral pigs – Bruce Watt (WRML, 2015)
- First human case of fatal Halicephalobus meningoencephalitis in Australia
- Ag now the biggest contributor to the Australian economy
- Is climate variability really on the rise?
WormFaxNSW-August / Outlook from the Outhouse
WormFax NSW is a summary of sheep WormTests from two of the major labs in NSW: The State Vet Lab and the Invetus (formerly VHR) lab in Armidale. The August edition is now up on the DPI website: http://www.dpi.nsw.gov.au/about-us/publications/wormfax
In summary, egg counts have been relatively low because we are coming out of winter and because it has been very dry over much of eastern Australia, and elsewhere. But, there have been occasional WormTest average egg counts >1500 eggs per gram of faeces. And this is an average; there will be individual animals with much higher counts. (A rule of thumb: two to a few times the average).
Remember also that sporadic worm crashes still happen in prolonged dry spells and droughts. This is one possible scenario: sheep are crowded onto a sacrifice paddock for supplementary feeding. Every so often there are scuds of rain and patchy storms. Little rivulets, carrying a lot of fresh manure, form. Then green ‘pick’ grows where the rivulets have run. Within several days, there are infective larvae aplenty, ‘climbing’ (swimming, actually) the green shoots. And the sheep ‘chase’ the green pick. If the producer has stopped regular WormTesting because ‘you don’t get worm problems in a drought’, there might be a ‘crash’, with very sick – even dead- wormy sheep. Emergency drenching then happens. And the drench may not be effective (due to drench resistant worms), because the producer has guessed what may be effective. (We are all human).
Other scenarios include chasing the remaining green pick along creeks with shady banks, and along bore drains, where there are some still remaining, or next to leaky irrigation channels or dams, or near permanent springs.
ParaBoss News – September 2017 – Feature Articles
Two of this month’s feature articles: see below
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Immunity loss at lambing and kidding
by Lewis Kahn, ParaBoss Executive Officer
‘Why are ewes and does more susceptible to worms in the last weeks of pregnancy and during lactation, and how does this influence management recommendations?’ >> Read more.
Flystrike Assist app
by Julia Smith, Development officer, DPIRD WA
‘The Flystrike Assist app, by the Department of Primary Industries and Regional Development in Western Australia, has been updated just in time for what is shaping up to be a busy flystrike season‘. >> Read more.
Macracanthorhynchus photos – Jayce Morgan, NSW DPI
Jayce Morgan is the Development Officer Pigs, Intensive Livestock Industries-Agriculture NSW, located at Tamworth, NSW. She recently sent me some pictures she took of Macracanthorhynchus hirudinaceus – the ‘thorny headed worm of pigs’, found in the proximal (upper) small intestine.
In Jayce’s pics below, the first shows the small intestine (SI), cut open in one place, and the (faintly striated/’wrinkled’) worm (sometimes mistaken for a tapeworm) exteriorised, but with the head still attached (leech-like) to the lining of the SI. The next shows (‘granulomatous’) nodules caused by the worm.
Image source/credit: Jayce Morgan
Image source/credit: Jayce Morgan
Acanthocephalans (thorny-headed worms, phylum Acanthocephala) are obligate endoparasites (i.e., internal parasites), ranging in size from 1 mm to over 40 cm. Acanthocephala is a separate phylum, closely related to Nematoda. They are called thorny headed worms because of the hooked-covered proboscis at the anterior end.
(‘Obligate’-having no options but one; ‘facultative’ -having more life choices. Similarly in bacteriology: e.g. facultative vs obligate anaerobes. Organisms all have their survival/reproductive strategies. Smart management (which might include coexistence) of troublesome organisms requires a good understanding of them. ‘Know your enemy’, as Sun Tzu (‘The Art of War’) said).
Image (somewhat magnified!)/source: Georgi’s Parasitology ..
Acanthocephalans have a two-host life cycle involving aquatic or terrestrial arthropods (intermediate host) and vertebrates (final or definitive host; usually in the host’s alimentary tract). The body of the adult worm is usually cylindrical, although some are flattened. The hollow proboscis, armed with hooks, which aids in attachment, is retractable, and lies in a sac. There is no alimentary canal; absorption takes place through the thick cuticle. The sexes are separate (dioecious), and males are much smaller than females. The eggs – resilient and produced in vast numbers (see Watt article) – are spindle- or oval-shaped, thick-shelled and contain a larva, which is called an acanthor due to its anterior circlet of spines and hooks. Once ingested by an arthropod intermediate host, the acanthor migrates to the haemocoel where it develops over 1-2 months into a cystacanth. The definitive host is infected by ingesting the intermediate host, and the cystacanth (a young adult), attaches in the alimentary tract where it matures, with females producing eggs after 5-12 weeks (the prepatent period). (Refs: 3,4,5).
The genera of veterinary importance are Macracanthorhynchus (pigs), Oncicola (dogs, other canids) and Prosthenorchis (Oncicola) (primates). (Ref: 4)
Macracanthorhynchus hirudinaceus (common name(s): “Giant Thorny-Headed Worm of swine”, or similar) adult worms are slightly curved white-pink (when fresh; and perhaps green-ish if stained by bile) and up to 10 cm (males) to 40-60 cm (females) long. (Oncicola canis is much smaller: about 6-14 mm long, and 2-4 mm wide). M hirudinaceus adults are thick, 5-10 mm wide, flattened, and have a cuticle that is transversely wrinkled. (This pseudo-segmentation makes them look similar to tapeworms). The adult worms resemble Ascaris suum, but taper posteriorly. There is no alimentary tract. There is a small proboscis at the anterior end. This is covered in about six transverse rows of hooks. The prepatent period is 2-3 months, and longevity is about one year. The large egg (~ 60 x 100 μm) is oval, symmetrical and has a thick grey-brown pitted shell. (Ref: 4).
M hirudinaceus is found worldwide, but not in some areas, eg western Europe. Light infections are usually asymptomatic; heavy infections may cause inappetance and weight loss. Diagnosis is based on finding the typical eggs in the faeces. At necropsy, the adults are Ascaris suum-like, but when placed in water, the tiny proboscis is protruded. The adults, using their proboscis, penetrate deep into the intestinal wall (duodenum; proximal small intestine). Heavy infections cause catarrhal enteritis. Occasionally perforation and even peritonitis ensue. Infection is seasonal (in the UK at least), partly due to availability of intermediate hosts. Eggs are viable in the environment for several years. (According to one source (Ref: 7), the worms are prolific egg layers but it is an uncommon parasite). Infection is most common in pigs 1-2 years of age. There is little information regarding treatment, but various sources ( Refs: 4, 8) state loperamide, levamisole and various macrocyclic lactones may be effective (sometimes as single treatments, sometimes as repeated treatments), although one source (Ref: 8) cites a reference (Primm, et al. 1992. Am. J. Vet. Res. 53:508-512) reporting variable efficacy of ivermectin. However, Ref: 1 says levamisole and ivermectin are effective for treatment. (Note that, in Australia, use of these drugs for this purpose may be off- or extra- label uses, i.e., requiring veterinary prescription or not permitted. In short, check the label). Control is by preventing access by pigs to intermediate hosts. This is most easily done in modern intensive rearing situations, but where pigs are kept in small sties, faces must be removed regularly to reduce the prevalence of dung beetles. (Ref: 4).
As stated, the definitive host for M. hirudinaceus (i.e., the host in which the parasite reaches maturity) is typically a pig (or other suids), and the predilection site is the small intestine. Carnivores and primates, very occasionally humans (see below) or dogs, may serve as accidental hosts. as mentioned, the parasite’s eggs are ingested by an intermediate host (typically a scarabaeoid or hydrophilid beetle (various dung/burrowing and water beetles)), which is subsequently eaten by the definitive host, resulting in infection of that host.
Macracanthorhynchus hirudinaceus is one of the two main acanthocephalans known to infect humans and cause acanthocephaliasis (the other being Moniliformis moniliformis). (Moniliformis generally infects rodents (Ref: 4). In infected human hosts, the worms seldom mature and, if they do, they generally do not produce eggs. Cases of acanthocephaliasis in humans (which are not very common as far as is known) generally occur in areas where insects are eaten for dietary or medicinal purposes. Nearly all known cases in humans have involved infection of the gastrointestinal tract, although Haustein et al. (2009) reported removing an immature unidentified acanthocephalan from a patient’s eye. (Refs: 3, 4, 5).
What’s in a name?
Acanth is from New Latin for ‘spine’ (hence ‘thorny); ‘cephala‘ means ‘head’; ancanthocephala means ‘thorny head; macracanthorhynchus means ‘giant thorny trunk’ (ref: 6). Hirudinea is a class of the phylum Annelida comprising the leeches. [From Latin hirūdo leech] (Source: Macquarie Dictionary). And ‘hirudotherapy’ is the medicinal use of leeches.
Macracanthorhynchus hirudinaceus, then, could be taken to mean ” leech-like and with a great thorny trunk (or perhaps head)” (‘Head’ seems to fit the morphology better).
Haemocoel: the primary body cavity of most invertebrates, containing circulatory fluid. From hemo- ‘of blood’ + Greek koilos ‘hollow, cavity.’ (Oxford Dict.) And, related to this, we have Latin coeliacus, from Greek koiliakos, from koilia ‘belly’; hence coeliac, which means, relating to the abdomen, or, relating to or affected by coeliac disease.
Proboscis: the nose of a mammal, especially when it is long and mobile such as the trunk of an elephant or the snout of a tapir. In many insects, an elongated sucking mouthpart that is typically tubular and flexible. In some worms, an extensible tubular sucking organ. Latin from Greek proboskis ‘means of obtaining food’, from pro ‘before’ + boskein ‘(cause to) feed’. (Oxford Dict.)
Dioecious: of a plant or invertebrate animal: having the male and female reproductive organs in separate individuals. Compare with monoecious. Latin Dioecia (a class in Linnaeus’s sexual system), from di- ‘two’ + Greek -oikos ‘house’. (Oxford Dict.)
Sources /more information:
- http://eol.org/pages/404600/overview (Encyclopedia of Life)
- Taylor’s Veterinary Parasitology (textbook; 4th ed).
- ‘Georgi’s’ Parasitology for Veterinarians (therefore highly simplified?? 🙂
Macracanthorhynchus hirudinaceus in feral pigs – Bruce Watt (2015)
Here is a nice article from Dr Bruce Watt (one of the many excellent LLS vets), written in 2015:
First human case of fatal Halicephalobus meningo encephalitis in Australia
Dr Jillian Kelly, a (NSW) Local Land Services District Veterinarian, came across this report in her reading:
Lim and others, 2015. See case report here http://jcm.asm.org/content/53/5/1768.full
Halicephalobus gingivalis is a free-living, saprophytic nematode with might be described as a facultative (opportunistic) neurotropic (nerve/brain-seeking) pathogen. It was first identified and named in 1954 (Stefanski). (For more info, see the links below).
It occurs sometimes in horses (and some other animals) in various parts of the world. (So far, I have found no evidence that it has been diagnosed in horses or other animals in Australia, but I could be wrong). And sometimes, apparently very rarely, it occurs in humans. Certainly confirmed cases are rare: the case that Lim and others describe, the first reported human case in Australia, is just the sixth human case described in the literature worldwide since 1975. Diagnosis antemortem is a challenge, as is treatment, due to the problem of getting large-ish molecules past the blood-brain barrier.
More information here:
Pintore MD and others, 2017: https://parasitesandvectors.biomedcentral.com/articles/10.1186/s13071-017-2070-3
saprophyte: a plant, fungus, or microorganism that lives on dead or decaying organic matter. (Oxford Dict).