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)
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”.
“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.”
‘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.
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.
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
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.
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