Paramphistomes or Stomach Fluke are prevalent in cattle throughout the coastal belt. During the writer's sojourn for a period of four years in the Casino District adult fluke were encountered frequently on post-mortem examination of cattle. The adult flukes inhabiting the rumen and recticulum apparently do not cause any ill effect to their host. Immature flukes, however, when the infestation is heavy enough, are responsible for mortality in young cattle. On one occasion massive infestation with immature paramphistomes was responsible for heavy mortality in adult milking cows.
Mortality in grown cattle, due to infestation with immature paramphistomes, is rare. An outbreak in a dairy herd was encountered by the writer and its history is the subject of this communication.
On the 22nd March, 1947, following a report that a mortality was occurring among milking cows, a visit was paid to the property. It was ascertained that the dairyman had only taken over this farm and moved his cattle there about three months previously. During the first week in March he had noticed that several of his cows commenced to fall away in condition and milk flow was reduced. At that time there were 45 cows in the herd. Three cows died between the 16th and 21st March and another died on the day of my visit. Examination of the herd showed that at least sixteen of the remaining animals were showing symptoms. Those affected were, with the exception of one aged cow, on their first or second lactation period.
Symptoms. Beside the loss of condition and reduced milk yield, the affected animals were dull and weak. There was a persistent foetid diarrhoea, often of watery consistency and showing evidence of intestinal haemorrhage. In the animals that had shown symptoms for some time anaemia was pronounced, as shown by the paleness of the visible mucous membranes and oedematous condition of the lower jaws. In the last stages of the condition the animals were very emaciated.
Post-mortem. Several carcases were examined. The striking feature was the massive infestation of immature paramphistomes. These parasites, small, reddish, oval bodies, about 1 mm. long, adhering to the mucous membrane, were present throughout the small and large intestine, caecum and abomasum. In the small intestine the infestation was heaviest, and in parts it was estimated that there were a dozen or more immature flukes per square inch of mucous membrane. Due to the irritation caused there was marked congestion of the bowel and numerous inflammatory foci associated with pitting of the membrane where the flukes were attached. A careful search of the rumen and reticulum in several post-mortems failed to reveal any mature parasites.
Treatment was generally unsatisfactory. If hexachlorethane had been available at the commencement of the mortality this would have been tried. For want of something better, the owner was immediately advised to drench his cattle with 4 ml. carbon tetrachloride (tetrachlorethylene was not obtainable) incorporated in liquid paraffin. It was considered not advisable to administer larger doses due to the enteritis present. Later a further dose of carbon tetrachloride was given. This treatment did not appear to have any definite beneficial effect and the mortality continued. Finally, after repeated attempts, a supply of hexachlorethane was obtained early in May from the Imperial Chemical Laboratories, but the mortality had now practically subsided and 14 cows had died. The cows, with the exception of one that previously had shown symptoms, now had ceased scouring and were stronger and improving in condition. The exception was a very weak cow and she was dosed with 50 gms. of hexachlorethane. 5 gms. bentonite and 75 ml. of water.
This cow was considered too weak to recover and later died.
The property on which the cattle were running was a mixture of poor, sandy ridge and heavy black soil creek flat. The latter land was typical north-coast "melon hole" country and had been flooded by summer rains. Much of it, when the mortality commenced, was little better than a swamp. To this the cows had daily access and undoubtedly picked up the infestation there. Search of this country on two occasions for the intermediate host of the paramphistomes failed to reveal any snails. However, in a channel nearby that drained this land. a plentiful supply of snails of the Bullinus spp. were found. An endeavour was made at Glenfield to ascertain whether these contained paramphistomes cercariae, but this was not successful.
On different occasions between the commencement of the outbreak in March and the middle of August, faecal samples were obtained from several cows in the herd, and at no time were any paxamphistome eggs recovered. It will be remembered that no mature parasites were detected on post-mortem examination. According to the literature, completion of the life cycle of Cotylophoron may take up to six months. These findings suggest that the infestation was recent. However, the absence of any mature paramphistornes was considered very unusual in view of their prevalence in coastal cattle. This factor may have played some part in the mortality. These animals probably had little resistance to the massive infestation of immature parasites due to not having built up an immunity as a result of previous light infestations.
On this property, whilst the mortality In the adult cattle was occurring, the calves did not do well and 8 died out of 23, although reasonably well-fed and cared for. The early deaths were apparently due to infestations of Trichostrongylus spp and the calves were drenched five times with Phenothiazine. Faecal samples taken from the calves in August disclosed low egg counts and later deaths were due to pneumo-enteric conditions. Contrary to what might be expected, post-mortem examination on several of these calves failed to reveal any paramphistomes. This probably is explained by the fact that they were run on the higher country all the time and were not given access to the swampy flat and the opportunity to pick up the cercariae.
(1) Infestation with immature paramphistornes caused serious mortality in milking cows; resulting in the death of 15 animals out of 41 in the herd.
(2) The absence of mature pramphistomes was considered most unusual; firstly in view of the massive infestation with immature parasites, secondly on account of the frequency with which these parasites are seen on post-mortem examination of coastal cattle.
(3) The resistance of the cattle was probably low, due to the fact that immunity had not been acquired by previous infestation.