HAEMATOLOGICAL … P. Niedźwiedzka-Rystwej
HAEMATOLOGICAL PATTERN IN RABBITS INFECTED WITH THREE STRAINS OF
Paulina Niedźwiedzka-Rystwej
Wiesław Deptuła
Department of Microbiology and Immunology,
Faculty of Natural Sciences, Szczecin University,
ul.Felczaka 3c, 71-412 Szczecin
e-mail:
ABSTRACT
The paper describes haematological pattern in rabbits infected with three strains of RHD (rabbit haemorrhagic disease) virus, that differs in biological traits, as they were one haemahhlutinating Italina reference strain BS89, one haemagglutinogenic German strain defined to represent an antigenic variant Triptis and one non-haemagglutinogenic English strain Rainham. The three strains of RHD virus were compared in terms of haematologic indices (haemoglobin concentration, numbers of erythrocytes, thrombocytes, total number of leukocytes, numbers of lymphocytes, neutrophils, eosinophils, basophils and monocytes). The obtained results showed that examined strains induced different pattern of haematological response, as the haemagglutinogenic reference strain of BS89 and the non-haemagglutinogenic Rainham strain of RHD virus induced alterations in haematological indices with a similar frequency while the haemagglutinogenic antigenic variant of RHD virus, Triptis induced very infrequently alterations in the examined haematological indices.
Key words: RHDV (rabbit haemorrhagic disease), haematological parameters
HAEMATOLOGICAL … P. Niedźwiedzka-Rystwej
INTRODUCTION
Haematological studies on haemoglobin concentration, numbers of erythrocytes, leukocytes and quality of blood smear conducted in the world pertained 8 haemagglutinogenic (Chinese, Austrian, Italian, German, Korean, Spanish, French and Israeli ones) strains of RHD virus. They included studies of a static character, mostly demonstrating decreased values in majority of studied variables, mainly lymphocytes and total number of leukocytes (cit.8). On the other hand, our national studies were conducted in a dynamic set-up and pertained 9 haematological indices (concentration of haemoglobin, numbers of erythrocytes and thrombocytes, total number of leukocytes and qualitative pattern of blood, including numbers of lymphocytes, neutrophils, eosinophils, basophils and monocytes) following infection with 12 French strains (Fr-1 i Fr-2) (11), 4 Czech strains (CAMP V-351, CAMP V-561, CAMP V-562 and CAMP V-558) (6) and 6 Polish strains (K-1 (9), SGM, MAŁ (11), KGM, Kr-1 (5) and one not closer defined strain (7)) of RHD virus. Also, the recent studies pertained only haemagglutinogenic strains and they did not include antigenic variants.
AIM
In view of the above presented facts present study aimed at monitoring haematologic indices (haemoglobin concentration, numbers of erythrocytes, thrombocytes, total number of leukocytes, numbers of lymphocytes, neutrophils, eosinophils, basophils and monocytes) in rabbits infected with 3 strains of RHD virus manifesting distinct biological properties, including the haemagglutinogenic Italian reference strain of BS89 (4), haemagglutinogenic German strain defined to represent an antigenic variant, Triptis (10) and the non-haemagglutinogenic English strain, Rainham (3).
HAEMATOLOGICAL … P. Niedźwiedzka-Rystwej
MATERIAL AND METHODS
The studies were conducted on 60 mixed breed rabbits of either sex and body weight ranging from 3.20 to 4.20 kg, classified as conventional animals (1). The animals originated from a certified breeding farm, remaining under permanent veterinary-zootechnical supervision and they were kept in a vivarium of the Chair of Microbiology and Immunology, Faculty of Natural Sciences, University of Szczecin, in which zootechnical parameters were consistent with the recommended standards. The animals were fed full-portion rabbit chow for rabbits (16% Królik from Motycz) and had an unrestricted access to water (2). The animals were alloted to three groups of infected rabbits. Group I of 10 rabbits was infected with the haemagglutinogenic Italian reference strain, BS89, manifesting HA titre of 10240, Group II of 10 rabbits received the non-haemagglutinogenic English strain of Rainham, while Group III of 10 rabbits received the haemagglutinogenic German strain Triptis of RHD virus, with HA titre of 2560. The animals were infected by intramuscular infection of respective viral strain, prepared in the form of 20% homogenate of rabbit liver, purified by centrifugation and chloroform treatment and suspended in 1 ml glycerol. Every group of infected animals was accompanied by a group of 10 control animals, which received intramuscular injection of 1 ml glycerol.
Blood for the studies was sampled from marginal ear vein in a rabbit in hour o (i.e. before antigen administration and, then, in hours 4,8,12,24 and 36 after infection, i.e. till the first signs of the disease appeared, in line with recommendations of the Local Ethical Commission in Szczecin. In blood of infected and control animals haematological indices were estimated, including haemoglobin concentration, numbers of erythrocytes, thrombocytes, leukocytes and blood smear (numbers of lymphocytes, neutrophilic, basophilic, acidophilic granulocytes and (cit. 6,8,11).
HAEMATOLOGICAL … P. Niedźwiedzka-Rystwej
RESULTS
Results obtained in this study are summed up in Table 1. Summing up the obtained results, the most frequent alterations were noted in number of thrombocytes while no alterations were detected in in numbers of erythrocytes, eosinophils, basophils and monocytes. Among the three examined strains of RHD virus the most frequent changes were induced by the haemagglutinogenic reference BS89 strain of RHD virus, followed by the non-haemagglutinogenic viral strain of Rainham while clearly the least frequent changes were detected following infection with the haemagglutinogenic antigenic variant of Triptis.
Summing up the results it should be concluded that changes in haemoglobin levels were induced only by the non-haemagglutinogenic Rainham strain of RHD virus. The changes manifested by an increase in hour 4 h and a decrease in hour 36 following administration of the antigen. As far as erythrocyte number was concerned, no alterations were detected following infection with any of the examined RHD viral strains (BS89, Rainham, Triptis), the thrombocyte numbers were decreased following infection with the haemagglutinogenic reference strain of BS89 (4,8,12,24 h) and the non-haemagglutinogenic Rainham strain (12,24,36 h), while the haemagglutinogenic antigenic variant, Triptis induced no changes in the variable. The general number of leukocytes demonstrated a decrease only following infection with the haemagglutinogenic reference BS89 strain (in hours 12 and 24) and following infection with the non-haemagglutinogenic strain of Rainham of RHD virus (in hour 24) while the haemagglutinogenic antigenic variant of RHD virus, Triptis induced no alterations in the variable. Lymphocyte number was decreased in hour 12 after administration of the haemagglutinogenic reference BS89 strain while both the non-haemagglutinogenic Rainham strain and the haemagglutinogenic antigenic variant of RHD virus, Triptis increased the number of lymphocytes in hour 36 following infection. Neutrophil level was increased only in hour 12 following administration of the haemagglutinogenic reference BS89 strain of RHD virus while the remaining two
HAEMATOLOGICAL … P. Niedźwiedzka-Rystwej
strains of the virus induced no alterations in the variable. Levels of eosinophils, basophils and monocytes manifested no changes following infection with any of the examined strains of RHD virus.
DISCUSSION
Analysis of the haematological results obtained following administration of the three RHD virus strains, the haemagglutinogenic BS89 references train, the non-haemagglutinogenic Rainham strain and the haemagglutinogenic antigenic variant of Triptis jusfied a conclusion that they resemble results obtained earlier following administration of two French strains, Fr-1 and Fr-2 (11), 4 Czech strains, CAMP V-351, CAMP V-561, CAMP V-562 and CAMP V-558 (6) and 5 Polish strains, K-1 (9), SGM, MAŁ (11), KGM and Kr-1 of RHD virus (5), which represent non-haemagglutinogenic strains and which do not represent antigenic variants.
Comparing the results obtained for haemoglobin levels, the absence of changes noted following the haemagglutinogenic reference BS89 strain and the haemagglutinogenic antigenic Triptis variant of RHD virus was also noted following administration of Fr-1, Fr-2 (11), CAMP V-562 (6), SGM, MAŁ (11) and Kr-1 (5) strains. On the other hand, the increase noted in hour 4 following infection with the non-haemagglutinogenic Rainham strain of RHD virus had no analogies in the earlier obtained results while the decrease noted in hour 36 following administration of the virus strain was identical to those obtained following administration of CAMP V-351 or CAMP V-561 (6). In general numbers of leukocytes the decrease noted in the level following the haemagglutinogenic reference strain of BS89 (12,24 h) or non-haemagglutinogenic Rainham strain (24 h) of RHD virus was analogous to those obtained following administration of CAMP V-561 strain (a decrease in hour 24) (6) and, partially, the results resembles those obtained following strains of MAŁ (11), KGM and Kr-1 (5), in the cases of which the decrease was noted in hours 52, 56 and 60 h following administration of the antigen, i.e. also at the end of the experiment,
HAEMATOLOGICAL … P. Niedźwiedzka-Rystwej
which in cases of the latter viral strain lasted till hour 60 and not, as it has been observed with the strains examined at present, till hour 36. The absence of changes in erythrocyte numbers following infection with the three currently examined strains of RHD virus confirmed the results earlier obtained for Fr-1, Fr-2 (11), CAMP V-562 (6), SGM, MAŁ (11), KGM and Kr-1 (5) strains. On the other hand, the decrease in thrombocyte number noted following the haemagglutinogenic reference strain of BS89 (4,8,12,24 h) and the non-haemagglutinogenic strain of Rainham (12,24,36 h) of RHD virus resembles the values earlier obtained for CAMP V-562 strain (a decrease in 4,8,12,24,36 h) and CAMP V-558 (a decrease in hours 24,36 h) (6). The absence of changes in thrombocyte numbers observed following the haemagglutinogenic antigenic variant of RHD virus, Triptis is analogous to alterations noted after administration of CAMP V-561 strain of RHD virus (6). As far as lymphocyte levels are concerned, the decrease in the index seen in 12 h following infection with the haemagglutinogenic reference BS89 strain of RHD virus resembles the results obtained earlier for CAMP V-562, CAMP V-558 (6) and MAŁ (11) strains, even if the alterations following the latter strains developed in later hours after the infection, i.e, respectively, in hours of 52, 48 and 36 h following administration of the virus. On the other hand, the increase in the parameter observed following administration of both the non-haemagglutinogenic strain of Rainham and the haemagglutinogenic antigenic variant of RHD virus, Triptis, in hour 36 after the infection resembles the increase noted following SGM strain (11), although, similarly to the earlier mentioned decrease, it wqas noted earlier, i.e. in hour 60 after the infection. The individual increase in neutrophil level in hour 12 following infection with the haemagglutinogenic references BS89 strain of RHD virus resembles only the increase in the parameter observed in hour 36 following administration of MAŁ strain of RHD virus (11), while the lack of alterations, observed following the non-haemagglutinogenic Rainham strain or the haemagglutinogenic antigenic variant of RHD virus, Triptis is analogous to that noted following administration of CAMP V-
HAEMATOLOGICAL … P. Niedźwiedzka-Rystwej
562 strain of RHD virus (6). On the other hand, the lack of alterations observed in levels of eosinophils. basophils and monocytes, recorded at present following administration of three currently examined strains (BS89, Raihnam, Triptis) of RHD virus resembles the pattern noted following administration of CAMP V-351, CAMP V-561 (6) and K-1 (9) strains.
SUMMARY
Summing up the results obtained following administration of three RHD virus strains of distinct biological properties, i.e. the haemagglutinogenic reference BS89 strain, the haemagglutinogenic reference antigenic variant of RHD virus, Triptis and the non-haemagglutinogenic Rainham strain, it can be concluded that the haemagglutinogenic reference strain of BS89 and the non-haemagglutinogenic Rainham strain of RHD virus induced alterations in haematological indices with a similar frequency while the haemagglutinogenic antigenic variant of RHD virus, Triptis induced very infrequently alterations in the examined haematological indices. The results might suggest that both haemagglutinogenic and non-haemagglutinogenic strain of the virus is capable of inducing numerous alterations in the haematological patterns while the antigenic variant induces no such changes, which possibly reflects the fact of antigenic variant development but it bears no relationship to heamagglutinogenic properties of the variant or their absence.
LITERATURE:
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HAEMATOLOGICAL … P. Niedźwiedzka-Rystwej
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Tab.1. Changes in haematological pattern in rabbits infected with three strains od RHD virus
RHD strainParameter / Haemagglutinogenic reference strain BS89 of RHD virus / Haemagglutinogenic
antigenic variant Triptis of RHD virus / Nonhaemagglutinogenic
strain Rainham of RHD virus
Haemoglobin concentration / bz / bz / ↑ 4
↓ 36
Number of erythrocytes / bz / bz / bz
Number of thrombocytes / ↑ -
↓ 4,8,12,24 / bz / ↑ -
↓ 12,24,36
Total number of leukocytes / ↑ -
↓ 12,24 / bz / ↑ -
↓ 24
Number of lymphocytes / ↑ -
↓ 12 / ↑ 36
↓ - / ↑ 36
↓ -
Number of neutrophils / ↑ 12
↓ - / bz / bz
Number of eozynophils / bz / bz / bz
Number of basophils / bz / bz / bz
Number of monocytes / bz / bz / bz
Legend: ↑/↓ – significant increase/decrese; bz – no changes detected; the numbers correspond to hours following infection at which the change was detected