THE IDENTIFICATION OF T A E N I A SPECIES FROM AUSTRALIAN CARNIVORES
I. BEVERIDGE", B.V.Sc.. Ph.D., and G. G . GRECORY~S, B.V.Sc. Introduction spp. including morphological features of the Increased interest in the epidemiology of mature proglottis not considered by Arundel taeniid cestode infections, due to the economic (1972a, b), a critical analysis of the methods significance of ovine cysticercosis, has resulted in used by this author and the presentation of data numbers of surveys to determine the incidence on hook sizes accumulated in a Tasmanian of various cestode species in wild and domesti- survey (Gregory 1973). cated carnivores in Australia (Jackson and Materials and Methods Arundel 1971; Broadbent 1972; Coman 1972a, Cestodes were obtained from various domesticated b, 1973; Gregory 1973; Dent and Kelly 1974). and feral carnivores in Victoria and Tasmania. Although a key to the species of cestodes occurIn Victoria, collections were made from rural dogs, ring in Australian dogs was provided by Arundel foxes and dingoes. Dogs were purged with arecoline and cestodes obtained were washed and (1972a, b), some difficulties have arisen with hydrobromide transported in normal saline with added antibiotics. respect to the specific identification of Taenia Foxes were shot a t night with th: aid of a spotlight, spp. and conflicting survey results have been their intestines were opened and any cestodes removed ascribed in part to possible inaccuracies in into normal saline. Cestodes were relaxed in water for identification (Coman 1973; Coman and Ryan several hours, fixed in 10% neutral formalin for 24-48 hr and stored either in formalin or 70% alcohol. A few 1974). specimens of each cestode species were fixed live in Whilst the four species of Taenia occurring in 10% formalin to determine the effects of severe conAustralian canids have been adequately described traction of the specimen on the various morphological examined. Cestodes from dingoes were taxonomically, information needed for identifica- characters obtained from Mr B. J. Coman, Victorian Dept. of tion is often scattered in the taxonomic literature Crown Lands and Survey and Mr L. K . Corbett, CSIRO and taxonomic revisions, although providing Division of Wildlife Research. The collection methods brief descriptions (Verster 1969) offer no key to for these latter specimens are as described by Coman the species and provide little indication as to the (1972b). In Tasmania, cestodes were collected from rural dogs reliability of the different morphological fcatures and submitted to the laboratory unpreserved as described useful in separating members of particular by Gregory (1973) and examined fresh. Whole strobilae or strobilar fragments were washed species groups. Furthermore, in large scale in tap water' for several hours, stained in 3% Mayer's surveys, because of the necessity of providing hnemalum overnight, dehydrated in alcohol, cleared in relatively rapid techniques of identification to be methyl salicylate and mounted in DePeX* or Canada able to process large quantities of material, or Balsam. Uterine branches were counted as recombecause suboptimal fixation techniques may limit mended by DuNoyer and Baer (1928) except that the main posterior bifurcations originating anterior to the morphological characteristics available for two the seminal receptacle were counted at lateral branches. examination, the process of identification may be Rostellar were removed under a dissecting microscope. limited to the examination of one or two features mounted in lactophenol or Berlese's fluid and digital only. There is no published information on the pressure applied to the cover-slip to force the hooks onto their sides. One large and one small rostellar hook relative reliability of single morphological criteria of each specimen were measured to the nearest Sum, in identifying species of Taenia present in Aus- as within-scolex variation has been shown to be insignificant (Clapham and Peters 1941; Beveridge 1974). tralia. Arundel (1 972a, b) has discussed the methods Remits of identification used in previous surveys and In Victoria, cestodes were examined from 30 provided a key based on rostellar hook lengths dingoes, 132 foxes and more than 100 rural and uterine branch numbers together with a dogs. T . pisiforrnis and T. serialis were found consideration of gross morphological features. in foxes, T . pisiformis, T . serialis, and T . hydaThe present paper reports on an analysis of tigena in dingoes and T . ovis, T . hydatigena, T . the various criteria available to identify Taenia serialis and T . pisiformis in rural dogs. In Tasmania from 1969-1974, 60,359 specimens of 'Department of Veterinary Paraclinical Sciences. Veterinary Clinical Centre, University of Melbourne, Werribee, Victoria, Taenia spp. were examined from 12,400 rural 3030 tDepartment of Agriculture. Launceston, Tasmania, 7250 *Address requests for reprints to G . G. Gregory.
Aiistraliari Vrteriiinry Journal, Vol. 5 2 , August, 1976
*
G . T. Gurr Ltd., London
369
dogs. Of these 46,271 were T . pisiformis, 9.040 T . hydatigena, 3,736 T . serialis and 1,272 T . ovis. Morphology of the Sexually Mature Proglottis The morphology of the mature proglottis was found to be a reliable means of identification, as shown in the following key: 1 . Testes confluent posterior - T . pisiformis to vitellaria Testes not confluent postenor to vitellaria - 2 2. Cirrus sac does not extend to the lateral osmoregulatory vessels - T . ovis Cirrus sec reaches lateral osmoregulatory vessels or extends beyond them into medulla - 3 3. Vaginal sphincter absent, - T . hydatigena testes in single layer Vaginal sphincter present, testes in several layers - T . serialis The testes of T . pisiformis lie in one to two dorso-ventral layers, those of T . ovis and T . hydatigena in a single layer and those of T . serialis in 2-4 layers. Only in T . pisiformis are the testes confluent posterior to the vitellaria. A vaginal sphincter is present only in T . ovis and T . serialis and the cirrus sac extends to or beyond the longitudinal osmoregulatory canals in all but T . ovis. In specimens severely contracted by fixation serial histological sections were necessary to determine the morphology of the vagina and cirrus sac, however, the relationship of the latter organ with the osmoregulatory canals was apparently not affected by fixation. Cross Strobilar Morphology After relaxation worms showed a characteristic proglottis and strobilar shape which was usually distorted in contracted specimens fixed alive. T . hydutigena is the broadest worm; its mature proglottides are rectangular, wider than long, and its gravid proglottides are square, or longer than wide. The strobila is straight-sided and the genital pores are inconspicuous. T . ovis is characterised by the convex sides of each proglottis giving the strobila a scalloped edge. Genital pores are obvious broad protrusions from the edges of the proglottides. The strobila often twists spirally whereas other species remain flat. 3 70
T . pisiformis is a narrow worm with elongate barrel-shaped proglottides which are narrower anteriorly. The genital pore is generally obvious and pointed. T . serialis is in many ways similar to T . pisiformis in strobilar morphology but is usually smaller. The large scolex and thick neck of T . pisiformis however differentiates it from the small globular scolex and long thin neck of T . serialis. Rostellar Hooks In the Tasmanian survey the first 30,000 worms were identified using rostellar hook length as the primary criterion. Frequency distributions of small sample of the large and small rostellar hook lengths are shown in Tables 1 and 2 respectively. It can be seen that large rostellar hook lengths are valuable in identifying most specimens of T . pisiformis, T . hydatigena and T . serialis although some overlap occurs between species. Small hook measurements are of limited use, except that those less than 100 p m can be identified as T . serialis. Large hooks, and sometimes also small hooks, may be lost from the scolex of unpreserved worms during collection requiring the use of alternative criteria. Measurements of large and small rostellar hooks cannot be used as two separate identification criteria as they are highly correlated across the range of the four species (r = 0.948). Uterine Branches In Table 3, comparative data are shown on the range of uterine branch numbers encountered in the present study and those of Verster (1969). There is overlap between all species thereby preventing the use of uterine branch numbers as an absolute criterion of identification. Minimum overlap ocurs between the species pairs T . hydatigena-T. ovis and T . hydatigena-T. serialis. Counting of uterine branches in several proglottides indicated that within-strobila variation can account for nearly 50% of the total variability shown in the uterine branch number of a population of T . pisiformis. Discurnion
A most reliable means of identification is by examination of the morphology of the mature proglottis since it provides several differentiating characteristics and since the characteristics occur in discrete rather than continuous states (e.g. the testes either are or are not confluent posterior to Australian Veterinary Journal, Vol. 52, August, 1976
TABLE 1 Frequency Distrihirtiou of /he Large Rostc~llurHook Lengths of 8063 Specitnetis of Taenia ~ p pCollected from TaSlrn~niLlnDogs Spccies
h
5
v
5 CD
3 Y
;
-L
m
0 y1
b
e! e,
F
2
360 275 270 265 260 255 250 245 240 235 230 225 220 215 210 205 200 195 190 185 180 175 170 165 160 155 150 145 140 135 130
T . pisiforrnis
No. Hooks Measured T . hydatigena
T . ovis
T . scrialis
I 1
22 79 C60 920 1938 916 837 46 8
3
-
5 110 126 469 3 13 359 120 57 7 9 2
2
1
20 26 93 30 36 2 3
5 53 205 320 153 91 11
3
Total no. hooks
5430
1581
210
842
Mean length & SD
249.8 & 6.4
205.7 & 7.9
178.7 2 6.3
149.7 & 5.8
the female genitalia). The technique is advan- of identification and form the basis of earlier. tageous in that cestode fragments can be identi- identification techniques (Jackson and Arundel fied, as well as immature worms, however, well 1971; Arundel 1972a, b; Coman 1973). The stained specimens are essential to determine the bifid nature of the small hook guard of T . anatomy of structures associated with the genital pisiformis, to distinguish between T . pisiformis atrium and the process of staining is time- and T . hydatigena (Hall 1919; Jackson and consuming. Furthermore, incompletely relaxed or Arundel 1917) was found in the present study poorly fixed specimens, particularly those fixed to be variable and of no diagnostic use. Some confusion apparently exists in the by immersion of whole gastro-intestinal tracts in formalin may be impossible to stain and examine separation of T . pisiformis and T . hydatigenu on satisfactorily (Coman 1973). With material of the basis of hook sizes and shapes. Jackson and the latter sort, identifications can be made from Arundel (1971) identified worms with large serial histological sections as live fixation hooks of 200 p m or more and a deeply bifid although causing contraction of the longitudinal small hook guard as T . pisiformis. However, a strobilar muscles does not seem to affect the third of their specimens of this species had relationship of the cirus sac with the osmoregu- hooks less than 220 pm, which, according to latory vessels, by causing the cirrus sac data on hook sizes presented here would render musculature to contract, however, the serial some of the identifications suspect. Arundel (1972a, b) has also quoted 210 p m as the sectioning probably has limited applicability. Of the various quanta1 characteristics, the minimum hook size for T . pisiformis, identifying rostellar hooks provide the more reliable method any specimens with hook sizes greater than 210 Australian Veterinary Journal, Vol. 52, August, 1976
37 1
TABLE 2 Freyi~ency Distribution of Small Rostellnr Hook Lengths f r o m 4,148 Specimens of Taenia s p p Collected front Tasmanimi Dogs
5
v
E ou c
i A
0
2
L
Species
T . pisiforniis
170 165 160 155 150 145 140 135 130 125 120 115
1 1 37 51 522 439 639 67 21
No. Hooks Measured T . Iiydatigenn
0 *
8
-*
IS 126 146 436 260 276 30 37 5
I 1
40 53 111 57 43 2
4
95 90 85 80 70
E
v)
1778
1346
Mean length t SD
144.7 t 5.6
137.8 t 7.7
p m as belonging to this species whilst Coman (1973) used 220 p m as the lower limit. In the present investigation, T. hydatigena was found with hook sizes up to 227 p m making the use by Coman (1973) of 220 p m as a cut off point more reliable than 200 p m or 210 p m which would lead to T. hydatigenu being misidentified as T . pisiformis. Frequency distributions of large rostellar hook lengths for the four species are Gaussian in form and the overlap occurring between adjacent species pairs provides obvious limits to the use of large hook sizes in identification. Whilst it may be possible on the basis of published ranges of measurements to select discrete limits for each species (Arundel 1972a, b), the fact that the frequency distributions are continuous suggests that hook lengths may occasionally lie outTABLE 3 Rnnge o j Uterine Brarich Numbers it1 Species of Taenia Occurring in A u s t r d i a ~~
~
Verster ( 1969)
T . nisiforrnis 8-16 T . j ~ y ~ ~ t i g e l ~ i r 5-10 T . ovis 10-30 T . seridis 8-18 372
2 35
60 23 3 200 138 9 8 1
Total no. hooks
Species
T . seriirlis
1 10
110 105 100
3
T . ovis
Present Study Victorian Tasmanian Specimens Specimens 5-19 3-9 8-17 8-13
9-1 5 3-9 14-30 11-23
308
11 9.9
* 6.5
686 97.0
* 5.2
side the recorded range. Hence the technique of identification based on large rostellar hook lengths alone is not entirely adequate. In spite of the limitations outlined above rostellar hooks can be extremely useful characters. They are not subject to fixation distortions, and even in -poorly preserved or macerated specimens, rostellar hooks can still be used for identification, One large hook measurement will give either a specific identification or limit the posibilities to two species. In recent years the use of uterine branch counts to identify Taenia spp has fallen into disrepute. Although identification of proglottides of T. suginatu and T . solium from humans had been based almost exclusively on uterine branch number, Verster (1967) showed that the hitherto unexpected variability led to a very high proportion of misidentifications and that a better system, based on the features of the genital atrium eliminated difficulties. Comparable findings with T. pisiformis indicated that when large numbers of specimens were examined the range of uterine branch number could be extended from the previously described 8-16 to 5-19. In consequence, uterine branch number is not a good criterion of identification of specimens. If the number of uterine branches was to be used, a mean of several proglottides Australian Veterinary Journal, Vol. 5 2 , August. 1976
within a strobila should be obtained rather than in water and then allowed to relax in water at the number in a single proglottis. Verster (1967) ambient temperature of 4°C up to 24 hours, showed not only that uterine branch numbers prior to fixation in formalin or alcohol. were variable but also that they could be difSummary ficult to count. Ova frequently aggregate in the An investigation into the reliability of various distal tips of branches, leaving the junction with the uterine stem very difficult to see. This dif- morphological criteria in differentiating species ficulty could account for the difkrences in of Tueniu in Australia showed that both the uterine branch number in T . ovis reported by anatomy of the mature proglottis and the gross morphology of the worms were reliable methods different sources shown in Table 3. The application of the various identification if suitably relaxed and fixed specimens were methods depends upon the circumstances under available. Measurements of rostellar hooks were which they are used. Jn the situation of a few useful but did not provide unequivocal identifiwell preserved specimens submitted for identifi- cation due to overlap in sizes; urine branch cation a combination of rostellar hook measure- numbers were found to be of little use. ments, gross morphology and mature proglottis Acknowledgments anatomy would give an unequivocal result. If Assistance with the identification of cestodes only gravid proglottides are available T . ovis and T . serialis can be identified on the anatomy in Tasmania was provided by R. M. Tyson, P. of the genital atrium, and gross morphology J. Kerr and W. Fulton. Finnacial assistance was then used to separate T . pisifortnis from T . provided by the Australian Meat Research liydatigetia. Arundel (1970) used gross pro- Committee. References glottis morphology and the number and form of utcrine branches to identify gravid proglottides Arundel, J. H . (1970)-Arrsf. i'rt. J. 46: 515. of T . ovis from a cat. A more certain identifi- Arundel, J. H . (1972a)--A.M.R.C. Rev. No. 4. Arundel, J. H. (1972b)--Artst. wf.J. 48: 140. cation could have been made from the features Beveridge, I. (1974)-Ph.D. Thesis. University of Melof genital atrium. bourne. For large scale surveys consideration should Broadbent, D. W. (1972)--Arr.rf. w. J. 48: 452. P. A . and Peters, B. G. ( 1941 ) - J . f f r l / r ~ i r ~ be given to identification methods prior to the Clapham, tlrol. 19: 75. collection of material, as live fixation of worms Coman, B. J. (1972a)--A1rst. iw. J. 48: 133. by preservation of the entire gastrointestinal Cornan, B. J. (1972b)-Aust. i*rr. J. 48: 456. tract or purge sample may force one to rely Coman, B. J. ( 1973)--Arr.sf. w t . J. 49: 378. B. J. and Ryan, G. E. (1974)--Arr.\t. I W . J. solely on rostellar hook lengths for identification Coman, 50: 577. (Coman 1973). For such a survey identification Dent, C. A. R. and Kelly, J. D. (1974)--Arrst. vet. J. can be made using gross strobila morphology as 50: 170. the main criterion with rostellar hook lengths DuNoyer, M. R. and Baer. J . G. (1928)--Bu/l. Sci. Phariiiucol. 4: 209. for support where necessary. Over 30,000 worms G. G. (1973)-Artst. vat. J. 49: 273. have been identified in Tasmania in this way. Gregory. Hall, M. C. (1919)-Pro~. U S . Not. M U S . 55: 1 . This system has been ignored in other surveys, Jackson. P. J. and Arundel. J. H. (1971 )--Artst. lief. J. 47: 46. mainly because of their methods of collection Verster, Anna (1967)-Z. Porusitrrot. 29: 313. and preservation of material. It is recommended Verster. Anna ( 1969~-Orirler.~icpoor1 J. vet. Rrs. 36: that worms removed from the gastro-intestinal 3. tract or from a purge sample be washed briefly ( R C C P ~ Vfor P ~prihliccrtiorr 2X Octohrr 1975 )
Aristrulirrir
Vclerirrciry Jourrial, Vol. 5 2 , August, 1976
I. BEVERIDGE", B.V.Sc.. Ph.D., and G. G . GRECORY~S, B.V.Sc. Introduction spp. including morphological features of the Increased interest in the epidemiology of mature proglottis not considered by Arundel taeniid cestode infections, due to the economic (1972a, b), a critical analysis of the methods significance of ovine cysticercosis, has resulted in used by this author and the presentation of data numbers of surveys to determine the incidence on hook sizes accumulated in a Tasmanian of various cestode species in wild and domesti- survey (Gregory 1973). cated carnivores in Australia (Jackson and Materials and Methods Arundel 1971; Broadbent 1972; Coman 1972a, Cestodes were obtained from various domesticated b, 1973; Gregory 1973; Dent and Kelly 1974). and feral carnivores in Victoria and Tasmania. Although a key to the species of cestodes occurIn Victoria, collections were made from rural dogs, ring in Australian dogs was provided by Arundel foxes and dingoes. Dogs were purged with arecoline and cestodes obtained were washed and (1972a, b), some difficulties have arisen with hydrobromide transported in normal saline with added antibiotics. respect to the specific identification of Taenia Foxes were shot a t night with th: aid of a spotlight, spp. and conflicting survey results have been their intestines were opened and any cestodes removed ascribed in part to possible inaccuracies in into normal saline. Cestodes were relaxed in water for identification (Coman 1973; Coman and Ryan several hours, fixed in 10% neutral formalin for 24-48 hr and stored either in formalin or 70% alcohol. A few 1974). specimens of each cestode species were fixed live in Whilst the four species of Taenia occurring in 10% formalin to determine the effects of severe conAustralian canids have been adequately described traction of the specimen on the various morphological examined. Cestodes from dingoes were taxonomically, information needed for identifica- characters obtained from Mr B. J. Coman, Victorian Dept. of tion is often scattered in the taxonomic literature Crown Lands and Survey and Mr L. K . Corbett, CSIRO and taxonomic revisions, although providing Division of Wildlife Research. The collection methods brief descriptions (Verster 1969) offer no key to for these latter specimens are as described by Coman the species and provide little indication as to the (1972b). In Tasmania, cestodes were collected from rural dogs reliability of the different morphological fcatures and submitted to the laboratory unpreserved as described useful in separating members of particular by Gregory (1973) and examined fresh. Whole strobilae or strobilar fragments were washed species groups. Furthermore, in large scale in tap water' for several hours, stained in 3% Mayer's surveys, because of the necessity of providing hnemalum overnight, dehydrated in alcohol, cleared in relatively rapid techniques of identification to be methyl salicylate and mounted in DePeX* or Canada able to process large quantities of material, or Balsam. Uterine branches were counted as recombecause suboptimal fixation techniques may limit mended by DuNoyer and Baer (1928) except that the main posterior bifurcations originating anterior to the morphological characteristics available for two the seminal receptacle were counted at lateral branches. examination, the process of identification may be Rostellar were removed under a dissecting microscope. limited to the examination of one or two features mounted in lactophenol or Berlese's fluid and digital only. There is no published information on the pressure applied to the cover-slip to force the hooks onto their sides. One large and one small rostellar hook relative reliability of single morphological criteria of each specimen were measured to the nearest Sum, in identifying species of Taenia present in Aus- as within-scolex variation has been shown to be insignificant (Clapham and Peters 1941; Beveridge 1974). tralia. Arundel (1 972a, b) has discussed the methods Remits of identification used in previous surveys and In Victoria, cestodes were examined from 30 provided a key based on rostellar hook lengths dingoes, 132 foxes and more than 100 rural and uterine branch numbers together with a dogs. T . pisiforrnis and T. serialis were found consideration of gross morphological features. in foxes, T . pisiformis, T . serialis, and T . hydaThe present paper reports on an analysis of tigena in dingoes and T . ovis, T . hydatigena, T . the various criteria available to identify Taenia serialis and T . pisiformis in rural dogs. In Tasmania from 1969-1974, 60,359 specimens of 'Department of Veterinary Paraclinical Sciences. Veterinary Clinical Centre, University of Melbourne, Werribee, Victoria, Taenia spp. were examined from 12,400 rural 3030 tDepartment of Agriculture. Launceston, Tasmania, 7250 *Address requests for reprints to G . G. Gregory.
Aiistraliari Vrteriiinry Journal, Vol. 5 2 , August, 1976
*
G . T. Gurr Ltd., London
369
dogs. Of these 46,271 were T . pisiformis, 9.040 T . hydatigena, 3,736 T . serialis and 1,272 T . ovis. Morphology of the Sexually Mature Proglottis The morphology of the mature proglottis was found to be a reliable means of identification, as shown in the following key: 1 . Testes confluent posterior - T . pisiformis to vitellaria Testes not confluent postenor to vitellaria - 2 2. Cirrus sac does not extend to the lateral osmoregulatory vessels - T . ovis Cirrus sec reaches lateral osmoregulatory vessels or extends beyond them into medulla - 3 3. Vaginal sphincter absent, - T . hydatigena testes in single layer Vaginal sphincter present, testes in several layers - T . serialis The testes of T . pisiformis lie in one to two dorso-ventral layers, those of T . ovis and T . hydatigena in a single layer and those of T . serialis in 2-4 layers. Only in T . pisiformis are the testes confluent posterior to the vitellaria. A vaginal sphincter is present only in T . ovis and T . serialis and the cirrus sac extends to or beyond the longitudinal osmoregulatory canals in all but T . ovis. In specimens severely contracted by fixation serial histological sections were necessary to determine the morphology of the vagina and cirrus sac, however, the relationship of the latter organ with the osmoregulatory canals was apparently not affected by fixation. Cross Strobilar Morphology After relaxation worms showed a characteristic proglottis and strobilar shape which was usually distorted in contracted specimens fixed alive. T . hydutigena is the broadest worm; its mature proglottides are rectangular, wider than long, and its gravid proglottides are square, or longer than wide. The strobila is straight-sided and the genital pores are inconspicuous. T . ovis is characterised by the convex sides of each proglottis giving the strobila a scalloped edge. Genital pores are obvious broad protrusions from the edges of the proglottides. The strobila often twists spirally whereas other species remain flat. 3 70
T . pisiformis is a narrow worm with elongate barrel-shaped proglottides which are narrower anteriorly. The genital pore is generally obvious and pointed. T . serialis is in many ways similar to T . pisiformis in strobilar morphology but is usually smaller. The large scolex and thick neck of T . pisiformis however differentiates it from the small globular scolex and long thin neck of T . serialis. Rostellar Hooks In the Tasmanian survey the first 30,000 worms were identified using rostellar hook length as the primary criterion. Frequency distributions of small sample of the large and small rostellar hook lengths are shown in Tables 1 and 2 respectively. It can be seen that large rostellar hook lengths are valuable in identifying most specimens of T . pisiformis, T . hydatigena and T . serialis although some overlap occurs between species. Small hook measurements are of limited use, except that those less than 100 p m can be identified as T . serialis. Large hooks, and sometimes also small hooks, may be lost from the scolex of unpreserved worms during collection requiring the use of alternative criteria. Measurements of large and small rostellar hooks cannot be used as two separate identification criteria as they are highly correlated across the range of the four species (r = 0.948). Uterine Branches In Table 3, comparative data are shown on the range of uterine branch numbers encountered in the present study and those of Verster (1969). There is overlap between all species thereby preventing the use of uterine branch numbers as an absolute criterion of identification. Minimum overlap ocurs between the species pairs T . hydatigena-T. ovis and T . hydatigena-T. serialis. Counting of uterine branches in several proglottides indicated that within-strobila variation can account for nearly 50% of the total variability shown in the uterine branch number of a population of T . pisiformis. Discurnion
A most reliable means of identification is by examination of the morphology of the mature proglottis since it provides several differentiating characteristics and since the characteristics occur in discrete rather than continuous states (e.g. the testes either are or are not confluent posterior to Australian Veterinary Journal, Vol. 52, August, 1976
TABLE 1 Frequency Distrihirtiou of /he Large Rostc~llurHook Lengths of 8063 Specitnetis of Taenia ~ p pCollected from TaSlrn~niLlnDogs Spccies
h
5
v
5 CD
3 Y
;
-L
m
0 y1
b
e! e,
F
2
360 275 270 265 260 255 250 245 240 235 230 225 220 215 210 205 200 195 190 185 180 175 170 165 160 155 150 145 140 135 130
T . pisiforrnis
No. Hooks Measured T . hydatigena
T . ovis
T . scrialis
I 1
22 79 C60 920 1938 916 837 46 8
3
-
5 110 126 469 3 13 359 120 57 7 9 2
2
1
20 26 93 30 36 2 3
5 53 205 320 153 91 11
3
Total no. hooks
5430
1581
210
842
Mean length & SD
249.8 & 6.4
205.7 & 7.9
178.7 2 6.3
149.7 & 5.8
the female genitalia). The technique is advan- of identification and form the basis of earlier. tageous in that cestode fragments can be identi- identification techniques (Jackson and Arundel fied, as well as immature worms, however, well 1971; Arundel 1972a, b; Coman 1973). The stained specimens are essential to determine the bifid nature of the small hook guard of T . anatomy of structures associated with the genital pisiformis, to distinguish between T . pisiformis atrium and the process of staining is time- and T . hydatigena (Hall 1919; Jackson and consuming. Furthermore, incompletely relaxed or Arundel 1917) was found in the present study poorly fixed specimens, particularly those fixed to be variable and of no diagnostic use. Some confusion apparently exists in the by immersion of whole gastro-intestinal tracts in formalin may be impossible to stain and examine separation of T . pisiformis and T . hydatigenu on satisfactorily (Coman 1973). With material of the basis of hook sizes and shapes. Jackson and the latter sort, identifications can be made from Arundel (1971) identified worms with large serial histological sections as live fixation hooks of 200 p m or more and a deeply bifid although causing contraction of the longitudinal small hook guard as T . pisiformis. However, a strobilar muscles does not seem to affect the third of their specimens of this species had relationship of the cirus sac with the osmoregu- hooks less than 220 pm, which, according to latory vessels, by causing the cirrus sac data on hook sizes presented here would render musculature to contract, however, the serial some of the identifications suspect. Arundel (1972a, b) has also quoted 210 p m as the sectioning probably has limited applicability. Of the various quanta1 characteristics, the minimum hook size for T . pisiformis, identifying rostellar hooks provide the more reliable method any specimens with hook sizes greater than 210 Australian Veterinary Journal, Vol. 52, August, 1976
37 1
TABLE 2 Freyi~ency Distribution of Small Rostellnr Hook Lengths f r o m 4,148 Specimens of Taenia s p p Collected front Tasmanimi Dogs
5
v
E ou c
i A
0
2
L
Species
T . pisiforniis
170 165 160 155 150 145 140 135 130 125 120 115
1 1 37 51 522 439 639 67 21
No. Hooks Measured T . Iiydatigenn
0 *
8
-*
IS 126 146 436 260 276 30 37 5
I 1
40 53 111 57 43 2
4
95 90 85 80 70
E
v)
1778
1346
Mean length t SD
144.7 t 5.6
137.8 t 7.7
p m as belonging to this species whilst Coman (1973) used 220 p m as the lower limit. In the present investigation, T. hydatigena was found with hook sizes up to 227 p m making the use by Coman (1973) of 220 p m as a cut off point more reliable than 200 p m or 210 p m which would lead to T. hydatigenu being misidentified as T . pisiformis. Frequency distributions of large rostellar hook lengths for the four species are Gaussian in form and the overlap occurring between adjacent species pairs provides obvious limits to the use of large hook sizes in identification. Whilst it may be possible on the basis of published ranges of measurements to select discrete limits for each species (Arundel 1972a, b), the fact that the frequency distributions are continuous suggests that hook lengths may occasionally lie outTABLE 3 Rnnge o j Uterine Brarich Numbers it1 Species of Taenia Occurring in A u s t r d i a ~~
~
Verster ( 1969)
T . nisiforrnis 8-16 T . j ~ y ~ ~ t i g e l ~ i r 5-10 T . ovis 10-30 T . seridis 8-18 372
2 35
60 23 3 200 138 9 8 1
Total no. hooks
Species
T . seriirlis
1 10
110 105 100
3
T . ovis
Present Study Victorian Tasmanian Specimens Specimens 5-19 3-9 8-17 8-13
9-1 5 3-9 14-30 11-23
308
11 9.9
* 6.5
686 97.0
* 5.2
side the recorded range. Hence the technique of identification based on large rostellar hook lengths alone is not entirely adequate. In spite of the limitations outlined above rostellar hooks can be extremely useful characters. They are not subject to fixation distortions, and even in -poorly preserved or macerated specimens, rostellar hooks can still be used for identification, One large hook measurement will give either a specific identification or limit the posibilities to two species. In recent years the use of uterine branch counts to identify Taenia spp has fallen into disrepute. Although identification of proglottides of T. suginatu and T . solium from humans had been based almost exclusively on uterine branch number, Verster (1967) showed that the hitherto unexpected variability led to a very high proportion of misidentifications and that a better system, based on the features of the genital atrium eliminated difficulties. Comparable findings with T. pisiformis indicated that when large numbers of specimens were examined the range of uterine branch number could be extended from the previously described 8-16 to 5-19. In consequence, uterine branch number is not a good criterion of identification of specimens. If the number of uterine branches was to be used, a mean of several proglottides Australian Veterinary Journal, Vol. 5 2 , August. 1976
within a strobila should be obtained rather than in water and then allowed to relax in water at the number in a single proglottis. Verster (1967) ambient temperature of 4°C up to 24 hours, showed not only that uterine branch numbers prior to fixation in formalin or alcohol. were variable but also that they could be difSummary ficult to count. Ova frequently aggregate in the An investigation into the reliability of various distal tips of branches, leaving the junction with the uterine stem very difficult to see. This dif- morphological criteria in differentiating species ficulty could account for the difkrences in of Tueniu in Australia showed that both the uterine branch number in T . ovis reported by anatomy of the mature proglottis and the gross morphology of the worms were reliable methods different sources shown in Table 3. The application of the various identification if suitably relaxed and fixed specimens were methods depends upon the circumstances under available. Measurements of rostellar hooks were which they are used. Jn the situation of a few useful but did not provide unequivocal identifiwell preserved specimens submitted for identifi- cation due to overlap in sizes; urine branch cation a combination of rostellar hook measure- numbers were found to be of little use. ments, gross morphology and mature proglottis Acknowledgments anatomy would give an unequivocal result. If Assistance with the identification of cestodes only gravid proglottides are available T . ovis and T . serialis can be identified on the anatomy in Tasmania was provided by R. M. Tyson, P. of the genital atrium, and gross morphology J. Kerr and W. Fulton. Finnacial assistance was then used to separate T . pisifortnis from T . provided by the Australian Meat Research liydatigetia. Arundel (1970) used gross pro- Committee. References glottis morphology and the number and form of utcrine branches to identify gravid proglottides Arundel, J. H . (1970)-Arrsf. i'rt. J. 46: 515. of T . ovis from a cat. A more certain identifi- Arundel, J. H . (1972a)--A.M.R.C. Rev. No. 4. Arundel, J. H. (1972b)--Artst. wf.J. 48: 140. cation could have been made from the features Beveridge, I. (1974)-Ph.D. Thesis. University of Melof genital atrium. bourne. For large scale surveys consideration should Broadbent, D. W. (1972)--Arr.rf. w. J. 48: 452. P. A . and Peters, B. G. ( 1941 ) - J . f f r l / r ~ i r ~ be given to identification methods prior to the Clapham, tlrol. 19: 75. collection of material, as live fixation of worms Coman, B. J. (1972a)--A1rst. iw. J. 48: 133. by preservation of the entire gastrointestinal Cornan, B. J. (1972b)-Aust. i*rr. J. 48: 456. tract or purge sample may force one to rely Coman, B. J. ( 1973)--Arr.sf. w t . J. 49: 378. B. J. and Ryan, G. E. (1974)--Arr.\t. I W . J. solely on rostellar hook lengths for identification Coman, 50: 577. (Coman 1973). For such a survey identification Dent, C. A. R. and Kelly, J. D. (1974)--Arrst. vet. J. can be made using gross strobila morphology as 50: 170. the main criterion with rostellar hook lengths DuNoyer, M. R. and Baer. J . G. (1928)--Bu/l. Sci. Phariiiucol. 4: 209. for support where necessary. Over 30,000 worms G. G. (1973)-Artst. vat. J. 49: 273. have been identified in Tasmania in this way. Gregory. Hall, M. C. (1919)-Pro~. U S . Not. M U S . 55: 1 . This system has been ignored in other surveys, Jackson. P. J. and Arundel. J. H. (1971 )--Artst. lief. J. 47: 46. mainly because of their methods of collection Verster, Anna (1967)-Z. Porusitrrot. 29: 313. and preservation of material. It is recommended Verster. Anna ( 1969~-Orirler.~icpoor1 J. vet. Rrs. 36: that worms removed from the gastro-intestinal 3. tract or from a purge sample be washed briefly ( R C C P ~ Vfor P ~prihliccrtiorr 2X Octohrr 1975 )
Aristrulirrir
Vclerirrciry Jourrial, Vol. 5 2 , August, 1976
