WRML.20131220. Wiley WormBoss, Sylvia Sykick and WormBoss News

The latest WormBoss news is out: http://www.wormboss.com.au/news.php

If you are a subscriber, you would have seen last month’s issue and become acquainted with Wiley WormBoss and Sylvia Sykick: http://www.wormboss.com.au/news/archives/november-2013.php

The latest lot of WormTest summaries are out (November) – see attached, and see notes at the website: http://www.dpi.nsw.gov.au/aboutus/resources/periodicals/newsletters/wormfax

In short, although it is very dry in parts of NSW, and worm egg counts in sheep (WECs) are often low, there are still some properties with high WECs. For example in the Central North LHPA and in the Armidale district, there are WECs ranging between 5,000 and 10, 000 epg.

If you need to drench, make sure the drench worked (DrenchCheckDay10 (in the case of roundworms in sheep/goats. (Day 14 for cattle, and day 21-28 for liver fluke (if using egg counts)). http://www.wormboss.com.au/tests-tools/tests/checking-for-drench-resistance.php
Bear in mind also that dry conditions might result in liver fluke disease on some properties with sheep ‘chasing green’ pick in gullies etc.

http://www.wormboss.com.au/worms/flukes/liver-fluke.php

http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0004/114691/liver-fluke-disease-in-sheep-and-cattle.pdf

Best wishes for Christmas and the New Year.

Regards,

SL

This message is intended for the addressee named and may contain confidential information. If you are not the intended recipient, please delete it and notify the sender. Views expressed in this message are those of the individual sender, and are not necessarily the views of their organisation. 

WormFaxNSW.2013-11.xls

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WRML More on condensed tannins and worm longevity. Liver fluke. Theileria. Bailey and Love

To WormMail list. (recip. undisclosed). cc Li G.

WRML.20131219. More on condensed tannins and on worm longevity. Liver fluke. Theileria. Bailey and Love.

More on condensed tannins

(Further to https://wormmailinthecloud.wordpress.com/2013/12/03/wrml-20131203-redux-overview-condensed-tannins-and-worm-control-also-scips-scops-wormboss/ )

Dr Johann Schröder (currently with Meat and Livestock Australia).

“There was fascinating work done in South Africa by Van Hoven et al. (early 1980s) which started when Kudu in small game reserves were seen to be losing condition. The discovery was that the browse which kudu feed on, has the ability to vary its tannin content. The plants push tannin into the leaves when they are disturbed, or attacked. This causes the browsing herbivore to take one mouthful and then move quite a distance before the next one – not so easy in small game reserves.

“The hypothesis was tested by measuring browse tannin content before and after whacking them with something like a tennis racquet or cricket bat. (Hence the proficiency of South Africans at sport? -Ed). It turned out that the plants are able to communicate with each other, so that if one plant pushes up its tannins, its immediate neighbours do too, thus necessitating the browsing animal to move on to more palatable feed.”

More on longevity of worms

(Further to https://wormmailinthecloud.wordpress.com/2013/12/03/wrml-20131202-how-long-do-sheep-worms-live/ )

Dr R Brown Besier (Western Australia)

“…. the life span of nematodes of ruminants depends mostly on immunity, as you say (Steve), but more specifically, the rate of larval intake, which of course influences immune effects. Also, it varies with species.

“Where there is no intake of 3rd stage larvae (L3), and moderate to low levels of infection, such as in animal house sheep, we keep infections of Teladorsagia and Haemonchus going for 6, even 8 months, but with diminishing and very variable egg counts.

“In the field in Western Australia, adult sheep carrying small worm burdens in late spring have similar-sized, or slightly lower, burdens in autumn if not summer-drenched. Under active field infection in worm-susceptible animals, I understand that Teladorsagia turns over quickly, i.e. adult worms are lost and new larvae establish, so that the life span is perhaps 3 weeks or less. However, Trichostrongylus (and I think Haemonchus) are different: adults remain and larvae fail to establish, although the life span of the adults is lower than where no L3s are being ingested.

“For farmer enquiries, we can assume that ruminants in the major agricultural zones are potentially continually infected with nematodes, due to continual intake where the environment or seasons allows L3 survival, or because adult worms can survive for some months where there is no active ingestion of L3s.

One parasite with a long life span is the liver fluke – the life time of the host, and Joe Boray reported one infection lasting 11 years”.

“PS. Hypobiosis is of course very well recognised in Haemonchus, both in very cold climates (Canada, Northern US, Norway …), and very dry ones (the Sahara, Middle East). But it is only for a few months before they have to face the cruel world again. Teladorsagia(sheep) and Ostertagia (cattle) are the only other ones we hear a lot about regarding hypobiosis, and surprisingly little about Trichostrongylus.

Dr Jan van Wyk, South Africa

“It is extremely difficult to estimate the survival ability of nematodes in animals under “natural” conditions. J.F. Michel (at the time at Weybridge in the UK) did a series of trials (in the 1980s?) to estimate the average survival time of Ostertagia ostertagi in cattle, using very large numbers of calves in the process.

“One problem is that dynamic exposure of the animals is required for realistic estimates, since it is clear from Michel’s work that continual challenge has a considerable effect on the longevity of the Ostertagia. If I remember correctly, he estimated the average survival in calves under continual challenge as 28 days, but this is bound to differ between worm species and especially genera. For instance, in the case of H. contortus hypermotility of the wall of the abomasum as a result of immunity leads to self-cure in some animals, and it has been demonstrated very well that some sheep also develop hyperimmunity to Teladorsagia, leading to serious diarrhoea after challenge with very small numbers of infective larvae, in relation to the numbers required for an equivalent effect on other sheep.

“Another problem is that one cannot distinguish worms of different generations over a single worm “infectious season”, which could very much simplify estimates of average survival ability. There have been attempts at labelling infective larvae with radioactive selenium and with Fe59, in which case we were able to follow the larvae produced by worms of sheep injected with the isotope, to adulthood (infective larvae from the eggs from the “radio-active” sheep used to infect naive lambs, with radiographic illustration of radio-activity in the adult H. contortus that developed from them), but nothing sufficiently practical for field use available to date.

“In contrast to the above, after many years of experience of laboratory maintenance of nematode pure strains with single exposure of animals bred and maintained under conditions of practically no unintentional worm infection, Reinecke (1973 – The Larval Anthelmintic Test in Ruminants. Technical Communication No. 106, Department of Agricultural Technical Services, Republic of South Africa, iii + 20 pp) published a list of periods of “maximum egg production” for common worm species (see table below).

“In the case of Schistosoma spp. infection in humans (I can’t remember whether it was S. mansoni and/or S. haematobium) there are well documented cases of survival of the worms for more than 30 years, with live eggs in the faeces and tissues after this period of time. Similarly, it is not uncommon for Fasciola spp. and Cotylophoron cotylophorum to “outlive” their host sheep in the respect that some of the latter remain infected after artificial exposure while young, with worm eggs continually passed in the faeces until they die of “old age” after periods of up to 8 years. “

“TABLE 1 – Periods of maximum worm egg production

[FROM: Reinecke (1973 – The
Larval Anthelmintic Test in Ruminants. Technical Communication No. 106,
Department of Agricultural Technical Services, Republic of South Africa,
iii + 20 pp)]   (See image/JPEG of table)

Reinecke-Per's-EggX'n GINem's-1973 via vanWyk 201312.-TABLE

Dr van Wyk added the following, notes he made working through the entire set of CAB’s “Helminthological Abstracts”, from the first volume, up to the mid to late ’80s,

“Below I copy a passage from the notes (not edited for this e-mail, and I’d have to look up the references listed if required). Furthermore, there is an Afrikaans word here and there, so please look past these little(?) “glitches”.

Cheers

Jan”

“FROM MY SET OF NOTES:

“Worm burdens are regulated principally by the short life of adult worms, … a population of O. ostertagi in a host acquiring new larvae at a constant rate, [being] in a state of equilibrium.” (Michel, 1982 – Symons, Donald & Dineen, bl 120). “From experiments in which groups of calves were dosed daily with infective larvae at different constant rates for up to 10 months, … Michel … showed that worm numbers rose to a plateau which was maintained for several months before falling. The height of the plateau was roughly proportional to the daily rate of larval intake. From a study of morphological changes, it was concluded that adult worms were being lost continuously and replaced by the development of incoming infective larvae or of arrested early fourth stage larvae (L4). … The occurrence of a turnover of adult worms was also supported by the continued presence of developing late L4 after adult worm numbers had ceased to increase. Although the mean length of life in the fifth stage did not alter with time, it was longer at lower infection rates – respectively 50 and 40 days at 200 and 340 larvae per day but 24 – 26 days at rates between 570 and 1600 larvae per day …” (Donald & Waller, 1982 – Symons Donald & Dineen – bl 172). Thus, the studies of Michel and co-workers have “established that O. ostertagi populations are regulated mainly by a continuous density-dependent loss of worms, combined with an increasing resistance to establishment of incoming larvae so that the rate of replacement of lost adults falls, which accounts for the ultimate decline of the adult population. The worm burden is not built up by an accumulation of ingested larvae but directly reflects the current rate of intake (Michel, 1969).” (Donald & Waller, 1982, referring to Michel, 1969 – In Symons, Donald & Dineen – bl 173). It should be kept in mind, however, that worms tend to live longer in hosts infested soon after birth (Michel, 1976 bl 363 & 364 -, referring to work by various investigators, using lambs and rats). ……. Michel (1976 – bl 376) found “… some evidence that the worm population is turned over more rapidly in older cattle than in calves.”

Liver fluke

‘Wet weather’ means ‘more worms/worm issues’, right?

Yes, but ….

Often fluke disease happens under drier conditions because livestock feed down into flukey areas chasing green pick.

So, not surprisingly:

“Liver Fluke has been identified as causes of illthrift and stock losses in New England authority area due to the previous dry start to spring and summer and stock grazing soaks and spring areas chasing green pick. (Veterinarians,) You may wish to remind your clients that their April and August drench program may also need a mid-summer fluke drench as well this year. “

Source: Dr Steve Eastwood, in NEW ENGLAND LHPA-VETERINARY PRACTITIONERS UPDATE DECEMBER 2013.

Theileria survey

Source: A survey to determine the prevalence of Theileria spp. in beefcattle in the northern tablelands of New South Wales
A Biddle, S Eastwood, L Martin, P Freeman and E Druce. Australian Veterinary Journal Volume 91, No 10, October 2013

The following is extracted from the paper:

Using a stratified random survey (46 beef herds), the authors aimed to estimate the within and between herd prevalences of Theileria orientalis in the eastern section of the New England Livestock Health and Pest Authority.

Blood samples were collected, packed cell volumes (PCV) were calculated, and numbers of Theileria organisms in blood smears counted.

Of the herds tested, 72% herd were positive for Theileria spp, showing infection is widespread in beef herds in the northern tablelands of New South Wales. (This perhaps is surprising given the colder winters of the New England – less hospitable for ticks – than the coastal areas to the east, for example).

Most (82%) herds had low or zero within-herd prevalence estimates, but a significant number had medium or high levels of Theileria.

A risk factor questionnaire suggested some associations, such as a link between tick treatment and Theileria detection.

Background

Infection of cattle by tick-borne protozoan parasites belonging to the Theileria orientalis group is common worldwide and has been detected in all Australian states except South Australia and
Tasmania. The organism may have been introduced to Australia with the tick Haemaphysalis longicornis from Japan in the early 1900s.

While endemic in cattle for some time, Theileria until recently has rarely been diagnosed as a cause of disease in Australian cattle. Since 2008, infection by organisms of the T. orientalis group has been identified as the cause of an increased number of cases of ill thrift and unexplained deaths in cattle across NSW.

Taxonomy of the group is debated, but for various reasons all are considered to belong to one species, T. orientalis.

However four types have been identified in the T. orientalis/buffeli complex:

type 1 (Chitose),
type 2 (Ikeda),
type 3 (Buffeli) and
type 4.

Research and investigation of cases involving infection with T. orientalis species in Australia has been ongoing.

In one report on eight cases, all were from coastal areas of NSW and five of the cases were in dairy herds. Outbreaks of the same syndrome have been confirmed in the northern tablelands of NSW in beef herds (New England Livestock Health and Pest Authority (LHPA), unpubl. data).

Seddon reported that 32% of 463 blood smears taken from cattle in NSW were positive for T. buffeli, but provided no details on the date, locations, herd prevalence or of the level of parasitaemia.

Significant outbreaks of clinical disease in cattle attributed to T. orientalis species have been reported recently in Victoria.

This study was to gain information about the prevalence and distribution of these ‘benign’ Theileria spp. in beef herds in the eastern section of the New England LHPA, an administrative area of approximately 3.6 million hectares on the northern tablelands of NSW. Awareness of theileriosis has increased and the condition of ‘bovine anaemia caused by T. orientalis group’ is now recognised, hence the importance of knowing the background level of Theileria infection in herds when interpreting diagnostic tests including blood smears in which T. orientalisis detected.

Bailey and Love: the dynamic duo

A few direct quotes from the website:

‘memorable anecdotes, and classic photographs make Bailey & Love a fascinating read’

‘Bailey & Love is the best there is’

‘beloved by generations’

‘Bailey & Love has a wide appeal’

http://www.baileyandlove.com/

Regards,

SL

This message is intended for the addressee named and may contain confidential information. If you are not the intended recipient, please delete it and notify the sender. Views expressed in this message are those of the individual sender, and are not necessarily the views of their organisation.

WRML.20131203. REDUX: Overview – condensed tannins and worm control. Also-SCIPS SCOPS WormBoss.

WormMail list (recip. undisclosed; cc Guangdi Li et al).

REDUX: Overview – condensed tannins and worm control

[Also: SCIPS (incl new technical manual),
SCOPS, WormBoss]

Feedback from Dr DM Leathwick, NZ:

‘I am less convinced of the ability of condensed tannins (CT) to suppress worm populations. Somewhat clearer however is their ability to reduce the symptoms of parasitism.

I was involved in a lot of the CT work done by John Niezen and Abdul Molan and, although there was an apparent reduction in faecal worm egg count (FEC) in nearly all cases, when we calibrated the FEC method to allow for the different composition of the faeces, the differences disappeared. Faeces from animals fed CT plants are quite different from those grazing more conventional pastures i.e. it is more difficult to float eggs out of faeces from CT fed animals.

We also did slaughter trials with CT plants which showed no difference in worm burden.

See:

Waghorn T.S., Molan A.L., Deighton M., Alexander R.A., Leathwick D.M., McNabb W.C. & Meagher L.P. 2006 In vivo anthelmintic activity of Dorycnium rectum and grape seed extract against Ostertagia (Teladorsagia) circumcincta and Trichostrongylus colubriformis in sheep. New Zealand Veterinary Journal, 54(1): 21-2

David Leathwick AgResearch, Palmerston North NZ.’

Robyn Neeson in her overview mentions that CTs can have variable effects and their modes of action with respect to worms or their consequences may vary.

Here is some of the discussion by Waghorn and others (2006):

‘One group of forage species which has received considerable attention from a parasite control perspective is the group of plants which contain moderate to high levels of CT. Extracts from plants (Athanasiadou et al 2000; Molan et al 2000ab, 2003ab; Hordegen et al 2003) and fresh forages (Niezen et al 2002a; Marley et al 2003ab; Min et al 2004) have been tested against a number of species of parasite either in vitro or in vivo.

However, results have not always been consistent between experiments (Butter et al 2001) and extracts which have shown promise in vitro have sometimes shown contradictory results in vivo (Athanasiadou et al 2001ab).

The effects of forages containing CT on gastrointestinal parasites have proved variable in sheep (Waghorn and Molan 2001; Niezen et al 2002ab), goats (Paolini et al 2003, 2005) and deer (Hoskin et al 2000). Reasons for this variation in activity include:

  • differences between continuous feeding or grazing (the usual field condition) and pulse or restricted feeding (the norm for indoor trials) (Athanasiadou et al 2001b);
  • different forages leading to different grazing habits and/or different distributions of parasitic larvae (Hutchings et al 2003);
  • CT binding to establishing third-stage larvae (L3), inhibiting motility (Hoskin et al 2000);
  • CT interfering with neurophysiology or neuromuscular coordination of parasitic larvae (Molan et al 2000a);
  • improved protein supply to the animal, possibly enhancing the immune response to parasites (Hoskin et al 2000);
  • CT requiring direct contact with the parasites (Butter et al 2001);
  • different chemical compositions of CT influencing efficacies (Molan et al 1999);
  • and different species of gastrointestinal parasites responding differently to CT (Molan et al 1999; Athanasiadou et al 2001a).’

SCOPs, which I will talk more about in a minute, has this to say about "Alternative and Bioactive Crops":

‘Grazing on bioactive forages, such as chicory, birdsfoot trefoil, and sainfoin has been shown to reduce the negative effects of parasitism in sheep, though we still have much to learn about their use in practical production systems. It is not yet known whether bioactive forages act directly against incoming or established worms or whether they work indirectly by improving the nutritional status of parasitised animals.’

Source: http://www.scops.org.uk/endoparasites-control-options.html

JN Bailey (Ph.D dissertation, University of New England, 2008) has this to say about condensed tannins:

‘Nutraceuticals are plants which produce secondary metabolites capable of anti-parasitic activity.

The majority of research in this field has focused on condensed tannins, with anthelmintic activity first reported in the early 1960s by Taylor & Murant (1966). Subsequent studies in sheep (Niezen et al., 1995; Niezen et al., 1998) have shown that grazing leguminous crops such as sulla, which are rich in condensed tannins, can result in reduced levels of GIN infection. Kahn & Diaz-Hernandez (1999) suggested that this response may be mediated by a direct (anthelmintic) effect on GIN viability or an indirect nutritional mechanism. In vitro and in vivo studies have provided evidence of a direct effect of condensed tannins against adult (Athanasiadou et al., 2000) and larval (Athanasiadou et al.,2001; Niezen et al., 2002; Brunet et al., 2007) stages of GIN parasites.

The indirect activity of condensed tannins against GIN parasites is facilitated by their ability to protect plant protein from ruminal digestion, thereby increasing the flow of nitrogen to the small intestine. The consequent nutritional benefit has been shown to increase levels of resistance and resilience to GIN parasites (Coop & Holmes, 1996). However, these benefits may be offset by anti-nutritional effects associated with condensed tannins such as reduction in feed intake, digestibility and rumen function (Jackson & Miller, 2006).

Additionally, the quality and quantity of secondary metabolites in plants is likely to be affected by variables such as soil type, season, cultivar and management (Thamsborg et al., 1999; Waller & Thamsborg, 2004). This adds to the difficulty of determining a dose response for, and practical integration of these control methods.

It is envisaged that suitable plants could be incorporated into permanent pasture or planted as a monoculture for use as a de-worming paddock (Niezen et al., 1998; Thamsborg et al., 1999; Coop & Kyriazakis, 2001). For this to be effective, in addition to anti-parasitic effects, the plants must be palatable, nutritious and able to withstand grazing. Ketzis et al. (2006) are of the opinion that at this point in time, there is no strong evidence to suggest that an economic benefit will accrue from consumption of condensed tannins by parasitized sheep. Comprehensive reviews of this subject have been conducted by (Hammond et al., 1997) and more recently by Githiori et al. (2006).’ (Used with permission).

SCIPS, SCOPS and WormBoss

‘SCIPS, SCOPS and WormBoss’ – ‘sounds like a bit of wordplay from a book for children.

WormBoss (wormboss.com.au) as you know was first launched in 2005, and then revitalised then re-launched on 21 November 2012 (21.11.12). If memory serves, work began on WormBoss around 2003, possibly earlier, under the leadership of Arthur Le Feuvre (with project oversight by RB Besier). (Subsequent leaders: Rob Woodgate, and then Lewis Kahn (current leader), with the WormBoss team being revitalized by new blood (L Kahn and Deb Maxwell) around 2011 or thereabouts).

Before WormBoss there was SCIPS and many of those involved with WormBoss also worked on SCIPS.

SCIPS stands for ‘sustainable control (of) internal parasites (of) sheep’. The SCIPS website (which was managed/developed by Dr Nick Sangster (then at Univ Sydney, now at CSU Wagga) – and colleagues) – and which was part of the SCIPS project – is still extant.

Here is the URL: http://sydney.edu.au/vetscience/sheepwormcontrol/ Although some of it is now out-dated, the website makes for informative/useful reading.

Work on SCIPS began around 1999/2000.

SCOPS (sustainable control of parasites of sheep), kicked off in Britain in 2003, with the website and associated materials appearing, I presume, a short time after.

That SCOPS sounds much like SCIPS is probably not a coincidence. Other unlikely coincidences are the fact that Dr Kym Abbott, one of the players in SCOPS, was at the University of Sydney about the same time as Nick Sangster. Kym then went to CSU Wagga, as did Nick (later). Kym is now at the new vet school at Roseworthy, South Australia. I am not suggesting anything untoward here. On the contrary, it just shows how widespread and beneficial various professional networks can be.

Here is the blurb on SCOPS from the (recently updated) 4th edition of the SCOPS technical manual [ http://www.scops.org.uk/vets-manual.html
]:

"SCOPS was formed in 2003 as the result of the industry and Defra recognising that we could not ignore this impending problem. The group is made up of representatives from across the sheep industry* working together to promote practical guidelines to sheep farmers and their advisers. These guidelines were originally produced as a result of a workshop held in March 2003, involving leading authorities in endoparasite control."

Updated SCOPS Technical Manual http://www.scops.org.uk/vets-manual.html

Well-known specialist sheep vet Dr John Plant let me know that the SCOPS tech. manual had been updated. See URL / link above.

It’s good reading. Read it in context however: general principles apply generally but some of the specifics vary from region to region.

For example, this news alert on the SCOPS website [ http://www.scops.org.uk/alerts-detail.php?AlertID=23
]:

"SCOPS Quarantine Recommendations – 13th September 2013

SCOPS has updated it’s recommendations for quarantine treatments to include resistant worms, sheep scab and the Barbers Pole worm (Haemonchus contortus):

Drench with either a 4-AD OR 5-SI drench + inject with 1% moxidectin

4-AD = Monepantel (Zolvix) ; 5-SI = Derquantel + abamectin (Startect) "

How does this relate to Australia? Well, given the prevalence of macrocyclic lactone resistance in Australia, this latest quarantine recommendation for the UK will be less than optimal in some situations in Australia.

Here is our current recommendation: See http://www.wormboss.com.au/programs/pastoral/managing-drench-resistance.php and http://www.wormboss.com.au/news/articles/drenches/quarantine-drenching-getting-it-right.php

Also, sheep scab was eradicated in Australia in the 19th century ( a bit of gratuitous/nationalistic bragging in lieu of consistent wins in cricket, rugby etc). The eradication of P. ovis was the genesis of the Pastures Protection Board system in NSW.

SCIPS or SCOPS?

SCIPS sounds a bit better to my unbiased ear: it evokes images of a frisky lamb (like those nice lambs at wormboss.com.au), unfettered by worminess, and ‘skipping’ or gambolling around a verdant paddock.

SCOPS sounds like a slightly dull lamb to me, with hang-dog appearance (listeriosis? PE? FSE?), and a slight scour developing, and maybe a touch of sheep scab. 🙂 (Ah, these antipodean colonials/ex-convicts!: they should show more respect).

SL.

20131203. e&oe

============

Previous WormMail on condensed tannins:

To WormMail list (recip. undisclosed). Overview – condensed tannins and worm control – Robyn Neeson [NSW DPI]

Robyn Neeson has prepared an overview of condensed tannins and worm control. It is republished here with permission.

Robyn is a Development Officer, Organic Farming, based at NSW Department of Primary Industries’ district office at Berry.

SL

This message is intended for the addressee named and may contain confidential information. If you are not the intended recipient, please delete it and notify the sender. Views expressed in this message are those of the individual sender, and are not necessarily the views of their organisation. 

Neeson R 2013 – condensed tannins- livestock nutrition and worms.Organic news Spring 2013.pdf

WRML.20131202. how long do sheep worms live?

WRML. how long do sheep worms live?

When asked how long adult roundworms (e.g. Haemonchus contortus) live in a sheep, I usually fudge with a suitably vague answer along the lines of:

‘ weeks to a few months depending on host immunity’

The question is actually more complicated. Is the question, ‘what is the maximal life span of worms?’ or is it ‘how long do worms usually live?’

In the chapter on Ageing in ‘Biology of Nematodes’ (Donald Lee (ed.). ISBN 0-415-27211-4), David Gems of University College, London discusses this topic at length.

I have not yet read the whole chapter as I feel I would need to devote a whole day to reading and comprehending it (with the prospect of forgetting it all in 3 minutes (EggTimers Disease)).

To give you an idea of the range of minimum estimates of adult longevity (with variable or unknown effects from host immunity, nematode aging etc) for various parasitic nematode species, I will quote some ranges from Table 17.2 in Gems’ chapter:

Ascarids: from 2-3 weeks, to 3-6 months (Toxocara canis (dogs)) to 1-2 years (Ascaris lumbricoides (humans)).

Spirurids (filarids): from 36 weeks (Dracunculus (ferrets)) to 13-16 years (Onchocerca, Wuchereria)

Strongloididae: from 2 days (S. stercoralis) to 55 weeks ( S. ratti)

Strongylida (‘hookworms’ (sic)): 16 days (Nippostrongylus brasiliensis (rats) to 32-100 weeks (Ancylostoma braziliense (cats), A. caninum (dogs) to more than 2 years (Haemonchus contortus (sheep)) to 8 years (Trichostrongylus (humans)), to 14-15 years for some hookworms in humans (Ancylostoma duodenale, Necator americanus).

HOWEVER….

Gems argues that 100 weeks for A. caninum and 32 weeks for A. braziliense are minimum estimates for potential life span and the same is likely to be the case in other strongylid parasites for animals, citing the example of Haemonchus contortus (much-loved by readers of WRML) in ruminants (principally sheep) where the length of patency varies with the intensity of the infections. Intense infections are cleared within 5 months, as a result of ‘self-cure’, whereas in sheep largely protected from reinfection, infections can last for more than 2 years.

A parasitologist (Sandground, 1936) self-infected with Trichostrongylus(possibly T. colubriformis) originating from Zimbabwe, found that egg-laying was undiminished 8.5 years after infection. I am sure that made for interesting dinner party conversations, especially if Sandground squirmed a little during the telling. The longevity of Trichostrongylus in sheep or other herbivores however might be somewhat different.

To read some interesting (I think) cases of trichostrongylosis in humans, see here: https://wormmailinthecloud.wordpress.com/2011/02/01/wormmail-20110201-trichostrongylosis-in-humans-redux/

(This Sandground story reminds me a little of Australian researcher Barry Marshall who infected himself with Helicobacter pylori in order to demonstrate its causative role in peptic ulcers (gastritis at least). H. pylori was isolated in Perth, Western Australia in ~ 1983 by Barry Marshall and Robin Warren (Warren often seems to get left out of this story, at least by the media).

(And, digressing briefly from nematodes, we all have read of course that the trematode Fasciola hepatica (liver fluke), can live for several years or more inside the liver of various hosts).

Here is SCOPS’ take (perhaps short-changing the worms a little??) on the matter:

http://www.scops.org.uk/endoparasites-worm-species.html

Regarding gastrointestinal nematodes (GINs) of sheep: ‘Adult worms that are not expelled by the immune system of the sheep or killed by anthelmintics will die naturally after a short period (typically less than 12 weeks).’

(Perhaps British worms are more delicate than the antipodean varieties).

Sutherland and Scott (2010), discuss the lifespan of parasitic nematodes:

* the longest nematode lifespans are for parasitic species. eg human hookworms: ~ 15 years (Gems is cited here); Dirofilaria immitis (heartworm of dogs) : as long as 7 years.

* however the important GIN species of livestock probably only live for a few months (with host immunity playing a role). (I guess ’12 weeks’ is roughly the same as ‘a few months’. – SL).

(Sutherland I and Scott I, 2010. Gastrointestinal nematodes of sheep and cattle: biology and control. (Wiley-Blackwell). ISBN 978-1-4051-8582-0)

So, overall, I am now a little happier with my equivocation: ‘ weeks to a few months depending on host immunity’. I think I can now call that an educated guesstimate.

How many worms?

I read somewhere (OK, it was wikipedia) that more than 28,000 species of nematodes have been described of which 16,000 are parasitic.

(Reference cited by wikipedia but not checked by me: Hugot J-P, Baujard P, Morand S (2001). “Biodiversity in helminths and nematodes as a field of study: an overview”. Nematology 3 (3): 199–208. )

Regards,

SL,

2013120211800

e&oe

“Few”

Although indefinite in nature, a few is usually more than two (two often being referred to as “a couple of”), and less than “several” (which is a number more than two or three but not very many ). If the sample population is say between 5 and 20, a few would mean three or four, but no more than this. However, if the population sample size were in the millions, “a few” could refer to several hundred items. In other words, few in this context means a very very small percentage but way over the 3 or 4 usually ascribed to it its use with much much smaller numbers.

So, I would take a few months to mean 3-4 months, perhaps even 3-5. 🙂

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